Reference
Manual
DOC. REV. 4/9/2013
VCM-DAS-3
Analog Output & Digital I/O
Module for the PC/104 Bus
as? RSALOGIC CORPORATION WWW.VERSALOGIC.COM
VCM-DAS-3 Reference Manual ii
WWW.VERSALOGIC.COM
12100 SW Tualatin Road
Tualatin, OR 97062-7341
(503) 747-2261
Fax (971) 224-4708
Contents Copyright ©2013
All Rights Reserved
Notice:
Although every effort has been made to ensure this document is error-free, VersaLogic makes no
representations or warranties with respect to this product and specifically disclaims any implied warranties
of merchantability or fitness for any particular purpose.
VersaLogic reserves the right to revise this product and associated documentation at any time without
obligation to notify anyone of such changes.
PC/104 and the PC/104 logo are trademarks of the PC/104 Consortium.
MVCMDAS3
VCM-DAS-3 Reference manual iii
Product Release Notes
Rev 2 Release
Production release.
Rev 1 Release
Alpha. No customer release.
Support Page
The VCM-DAS-3 support page, at http://www.VersaLogic.com/private/vcmdas3support.asp, contains
additional information and resources for this product including:
Reference Manual (PDF format)
Operating system information and software drivers
Data sheets and manufacturers’ links for chips used in this product
BIOS information and upgrades
Utility routines and benchmark software
Note: This is a private page for VCM-DAS-3 users that can be accessed only be entering this address
directly. It cannot be reached from the VersaLogic homepage.
VCM-DAS-3 Reference Manual iv
Contents
Introduction ................................................................................................................... 1
Description .......................................................................................................................... 1
Technical Specifications ..................................................................................................... 2
RoHS Compliance .............................................................................................................. 3
About RoHS ........................................................................................................... 3
Warnings ............................................................................................................................. 3
Electrostatic Discharge .......................................................................................... 3
Technical Support ............................................................................................................... 4
Repair Service ........................................................................................................ 4
Physical Description ..................................................................................................... 5
Dimensions ......................................................................................................................... 5
Side Profile ............................................................................................................ 6
External Connectors ........................................................................................................... 6
Connector Locations .............................................................................................. 6
Connector Functions and Interface Cables ............................................................ 7
J1 I/O Connector .................................................................................................... 8
J2 I/O Connector .................................................................................................... 9
J3 I/O Connector .................................................................................................. 10
Installation ........................................................................................................................ 11
Hardware Assembly ............................................................................................. 11
Stack Arrangement Example ............................................................................... 11
Configuration ............................................................................................................... 12
Jumper Blocks .................................................................................................................. 12
Jumpers As-Shipped Configuration ..................................................................... 12
Jumper Summary ................................................................................................. 13
Base Address Configuration ............................................................................................. 14
Bit Mode Configuration .................................................................................................... 15
Enhanced Mode Configuration ......................................................................................... 16
Power-up Span Range Configuration ............................................................................... 16
Registers ...................................................................................................................... 17
I/O Port Mapping .............................................................................................................. 17
I/O Port Register Functions ................................................................................. 18
Enhanced Mode Registers ................................................................................................ 19
Enhanced Control Register .................................................................................. 19
Enhanced Mode Data Registers ........................................................................... 20
Digital I/O Control Register ............................................................................................. 21
Digital I/O Data Registers ................................................................................................ 22
Digital Input Registers ......................................................................................... 22
Digital Output Registers ...................................................................................... 23
External Trigger Enable Register ..................................................................................... 24
Analog Output Data Registers .......................................................................................... 25
Contents
VCM-DAS-3 Reference manual v
DAC Channel Select Register ............................................................................. 25
DAC Write Registers ........................................................................................... 26
DAC Read Registers ............................................................................................ 26
Analog Output ............................................................................................................. 27
Analog Output Ranges and Resolution ............................................................................. 27
Setting a Span Range ........................................................................................... 27
Analog Output Data Representation ................................................................................. 28
Straight Binary Coding ........................................................................................ 28
Offset Binary Coding ........................................................................................... 29
Analog Output Programming ............................................................................................ 31
External Trigger Update ...................................................................................... 31
Load DAC Operation ........................................................................................... 31
Analog Output Code Example .......................................................................................... 32
Calibration ........................................................................................................................ 34
Setting the Gain ................................................................................................... 34
Reading the Gain ................................................................................................. 34
Enhanced Mode Operations .............................................................................................. 35
Reading DAC Data .............................................................................................. 35
Reading the Span of a Channel ............................................................................ 35
Setting a Channel to Sleep Mode ........................................................................ 36
Reading the Sleep Status of a Channel ................................................................ 36
Digital I/O ..................................................................................................................... 37
Signal Direction ................................................................................................................ 37
Signal Polarity .................................................................................................................. 37
Digital Input ...................................................................................................................... 37
Digital Output ................................................................................................................... 37
References ................................................................................................................... 38
VCM-DAS-3 Reference Manual 1
Introduction
Description
The VCM-DAS-3 is a PC/104-format data acquisition board that provides analog outputs and
digital I/O for process control and other applications. Its features include:
16 analog voltage outputs with 12-bit
resolution
Multiple output ranges
Software adjustable output ranges per
channel
Simultaneous or individual DAC
update
Power-up ranges set by jumpers in
groups of eight, reset per channel by
software
The VCM-DAS-3 module provides 16 single-ended analog outputs and 24 digital I/O channels.
Fully compatible at the register and connector level with the Diamond Systems Ruby-MM DAC
board, VCM-DAS-3 also provides enhanced mode operation that extends its capabilities. In
enhanced mode:
Analog output ranges can be set for individual channels through software.
Analog output and ranges can be read from individual channels.
Specific analog channels can be placed into sleep mode to conserve power.
Individual channels can be updated and read.
Calibration can be performed with software.
1 1
Technical Specifications
VCM-DAS-3 Reference Manual 2
Technical Specifications
Specifications are typical at 25°C with 5.0V supply unless otherwise noted.
Board Size: 3.55” x 3.775” (PC/104 standard)
Storage Temperature:
-40° C to +85° C
Operating Temperature:
-40° C to +85° C
Power Requirements:
5V
10%
Analog Output:
Channels: 16 outputs
Resolution: 12 bits
Output Ranges: Bipolar: ±10V, ±5V, ±2.5V, -2.5V to 7.5V
Unipolar: 0 - 10V, 0 - 5V
Output Current: ±5 mA max per channel
Settling Time: 8 uS Typ. (±10V Range, 20V Step to ±1LSB)
Accuracy: ±1 LSB
Integral
Nonlinearity: ±1 LSB
Differential
Nonlinearity: ±1 LSB
Calibration: One gain and one zero adjustment for all channels
Gain Temp.
Coefficient: ±2 ppm/° C
Update Method: Simultaneous, individual, or external trigger
Reset: Outputs reset to 0V when board is jumpered for Enhanced Mode,
mid-scale otherwise
Digital I/O:
Channels: 24
Compatibility: CMOS / TTL, 82C55 Mode 0 only
Low Input Voltage: -0.3V min., 0.8V max
High Input Voltage: 2.0V min., 5.5V max.
Low Output
Voltage: 0.4V max.
High Output
Voltage: 3.0V max.
Output Current: +4 mA / -8 mA max.
Pull-up Resistor: 10 K Ohm
Reset: All channels set to input mode
Software:
Operating Systems: Compatible with most X86 operating systems including
Windows 95/85/NT/CE/XP, QNX, VxWorks, and Linux
Driver Support: No native drivers. Fully compatible with Diamond Systems drivers.
Compatibility:
PC/104 Full compliance, 8-bit and 16-bit
Weight:
0.152 lbs (0.069 kg)
Specifications are subject to change without notice.
RoHS Compliance
VCM-DAS-3 Reference Manual 3
RoHS Compliance
The VCM-DAS-3 is RoHS-compliant.
ABOUT ROHS
In 2003, the European Union issued Directive 2002/95/EC regarding the Restriction of the use of
certain Hazardous Substances (RoHS) in electrical and electronic equipment.
The RoHS directive requires producers of electrical and electronic equipment to reduce to
acceptable levels the presence of six environmentally sensitive substances: lead, mercury,
cadmium, hexavalent chromium, and the presence of polybrominated biphenyls (PBB) and
polybrominated diphenyl ethers (PBDE) flame retardants, in certain electrical and electronic
products sold in the European Union (EU) beginning July 1, 2006.
VersaLogic Corporation is committed to supporting customers with high-quality products and
services meeting the European Union’s RoHS directive.
Warnings
ELECTROSTATIC DISCHARGE
Warning! Electrostatic discharge (ESD) can damage circuit boards, disk drives and other
components. The circuit board must only be handled at an ESD workstation. If an
approved station is not available, some measure of protection can be provided by
wearing a grounded antistatic wrist strap. Keep all plastic away from the board,
and do not slide the board over any surface.
After removing the board from its protective wrapper, place the board on a
grounded, static-free surface, component side up. Use an antistatic foam pad if
available.
The board should also be protected inside a closed metallic anti-static envelope
during shipment or storage.
SuyyonCIDVersuLOVianm http://www. VersaLoqic. com/pri vate/vcmdasé‘support. asp
Technical Support
VCM-DAS-3 Reference Manual 4
Technical Support
If you are unable to solve a problem after reading this manual please visit the VCM-DAS-3
Product Support web page at http://www.VersaLogic.com/private/vcmdas3support.asp. If
you have further questions, contact VersaLogic technical support at (503) 747-2261. VersaLogic
technical support engineers are also available via e-mail at Support@VersaLogic.com.
REPAIR SERVICE
If your product requires service, you must obtain a Returned Material Authorization (RMA)
number by calling (503) 747-2261. VersaLogic’s standard turn-around time for repairs is five
working days after the product is received.
Please provide the following information:
Your name, the name of your company and your phone number
The name of a technician or engineer that can be contacted if any questions arise.
Quantity of items being returned
The model and serial number (barcode) of each item
A detailed description of the problem
Steps you have taken to resolve or recreate the problem
The return shipping address
Warranty Repair All parts and labor charges are covered, including return shipping
charges for UPS Ground delivery to United States addresses.
Non-warranty Repair All non-warranty repairs are subject to diagnosis and labor charges,
parts charges and return shipping fees. Please specify the shipping
method you prefer and provide a purchase order number for invoicing
the repair.
Note: Please mark the RMA number clearly on the outside of the box before
returning.
VCM-DAS-3 Support Website
http://www.VersaLogic.com/private/vcmdas3support.asp
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VCM-DAS-3 Reference Manual 5
Physical Description
Dimensions
The VCM-DAS-3 complies with all PC/104 standards. Dimensions are given below to help with
pre-production planning and layout.
Figure 1. Dimensions and Mounting Holes
(Not to scale. All dimensions in inches.)
2 2
3.375
0.00
0.15
3.05
0.1875
0.00
3.15
3.3625
3.575
-0.20
= Pin 1
.06 1 z I as so 4 Al4.|v 0 EEE
External Connectors
VCM-DAS-3 Reference Manual 6
SIDE PROFILE
Figure 2. Side Profile
(Not to scale. All dimensions in inches.)
External Connectors
CONNECTOR LOCATIONS
Figure 3. Connector Locations (Top)
(Not to scale.)
J2
J1
J3
J4
= Pin 1
J5
B1
A1
C0
D0
C19
D19
49 50
1 2
B32
A32
1
1
2
2
9
39
10
40
V1
V2
V3
0.44
0.44
0.06
I=Pin1
External Connectors
VCM-DAS-3 Reference Manual 7
Figure 4. Connector Locations (Bottom)
(Not to scale.)
CONNECTOR FUNCTIONS AND INTERFACE CABLES
Table 1 provides information about the function, mating connectors, and transition cables for
VCM-DAS-3 connectors. Page numbers indicate where a detailed pinout is available.
Table 1: Connector Functions and Interface Cables
Connector
Function
Mating Connector
Transition Cable
Cable Description
Page
J1
Digital I/O (A0-
A7)
FCI 89361-710LF
2mm 10-pin IDC
8
J2
Analog Outputs,
Digital I/O (B0-
C7)
FCI 89361-740LF
CBR-4004A
12” 2mm 40-pin to
40-pin IDC to screw
terminal board CBR-
4004B
9
J3
Analog Outputs,
Digital I/O
Standard 0.150-pin
cable-mount IDC
Diamond Systems
C-50-18
Data acquisition, 50
conductor 0.1" ribbon
cable
10
J4
Factory use only
J5
PC/104
AMP 1375795-2
= Pin 1
PC/104 (ISA)
pass-through male
B1
A1
C0
D0
C19
D19
B19
A19
External Connectors
VCM-DAS-3 Reference Manual 8
J1 I/O CONNECTOR
The J1 I/O connector incorporates digital I/O signals A0 through A7. The pinout of the connector
is shown in Table 2.
Table 2 J1 I/O Connector Pinout
J1 Pin
Signal
Name
Function
1
Ground
Ground
2
DIO A7
Digital I/O A7
3
DIO A6
Digital I/O A6
4
DIO A5
Digital I/O A5
5
DIO A4
Digital I/O A4
6
DIO A3
Digital I/O A3
7
DIO A2
Digital I/O A2
8
DIO A1
Digital I/O A1
9
DIO A0
Digital I/O A0
10
Ground
Ground
External Connectors
VCM-DAS-3 Reference Manual 9
J2 I/O CONNECTOR
The J2 I/O connector incorporates analog voltage outputs 0 through 15 and digital I/O channels
B0 through C7. Table 3 illustrates the function of each pin and the pinout assignments to
connectors on the CBR-4004 I/O board.
Table 3: J2 I/O Connector Pinout
J2
Pin
Signal Name
Function
CBR-4004
Connector
CBR-4004
Pin (Label)
1
VOUT 00
Analog Out Ch 0
J1
5 (IO1)
2
VOUT 01
Analog Out Ch 1
Analog
4 (IO2)
3
VOUT 02
Analog Out Ch 2
Output
3 (IO3)
4
VOUT 03
Analog Out Ch 3
2 (IO4)
5
Ground
Ground
1 (GND1)
6
VOUT 04
Analog Out Ch 4
J2
5 (IO5)
7
VOUT 05
Analog Out Ch 5
Analog
4 (IO6)
8
VOUT 06
Analog Out Ch 6
Output
3 (IO7)
9
VOUT 07
Analog Out Ch 7
2 (IO8)
10
Ground
Ground
1 (GND1)
11
VOUT 08
Analog Out Ch 8
J3
5 (IO9)
12
VOUT 09
Analog Out Ch 9
Analog
4 (IO10)
13
VOUT 10
Analog Out Ch 10
Output
3 (IO11)
14
VOUT 11
Analog Out Ch 11
2 (IO12)
15
Ground
Ground
1 (GND2)
16
VOUT 12
Analog Out Ch 12
J4
5 (IO13)
17
VOUT 13
Analog Out Ch 13
Analog
4 (IO14)
18
VOUT 14
Analog Out Ch 14
Output
3 (IO15)
19
VOUT 15
Analog Out Ch 15
2 (IO16)
20
Ground
Ground
1 (GND2)
21
DIO B7
Digital I/O B7
J6
5 (IO17)
22
DIO B6
Digital I/O B6
Digital I/O B
4 (IO18)
23
DIO B5
Digital I/O B5
3 (IO19)
24
DIO B4
Digital I/O B4
2 (IO20)
25
Ground
Ground
1 (GND3/PBRST#)
26
DIO B3
Digital I/O B3
J7
5 (IO21)
27
DIO B2
Digital I/O B2
Digital I/O B
4 (IO22)
28
DIO B1
Digital I/O B1
3 (IO23)
29
DIO B0
Digital I/O B0
2 (IO24)
30
Ground
Ground
1 (GND3)
31
DIO C7
Digital I/O C7
J8
5 (IO25)
32
DIO C6
Digital I/O C6
Digital I/O C
4 (IO26)
33
DIO C5
Digital I/O C5
3 (IO27)
34
DIO C4
Digital I/O C4
2 (I028)
35
Ground
Ground
1 (GND4)
36
DIO C3
Digital I/O C3
J9
5 (IO29)
37
DIO C2
Digital I/O C2
Digital I/O C
4 (IO30)
38
DIO C1
Digital I/O C1
3 (IO31)
39
DIO C0
Digital I/O C0*
2 (IO32)
40
Ground
Ground
1 (GND4)
* Pin 39 can also used as an external trigger for updating DAC channels. See External
Trigger Update.
External Connectors
VCM-DAS-3 Reference Manual 10
J3 I/O CONNECTOR
The J3 I/O connector incorporates analog voltage outputs 0 through 15 and digital I/O channels
A0 through C7. The pinout of the connector is shown in Table 4.
Note This connector is compatible with Diamond Systems’ cable C-50-18. Any standard
0.1” 50-pin cable-mount IDC connector will mate with this connector.
Table 4: J3 I/O Connector Pinout
J3
Pin
Signal Name
Function
J3
Pin
Signal Name
Function
1
Ground
Ground
26
DIO A6
Digital I/O A6
2
VOUT 00
Analog Output 0
27
DIO A5
Digital I/O A5
3
Ground
Ground
28
DIO A4
Digital I/O A4
4
VOUT 01
Analog Output 1
29
DIO A3
Digital I/O A3
5
Ground
Ground
30
DIO A2
Digital I/O A2
6
VOUT 02
Analog Output 2
31
DIO A1
Digital I/O A1
7
Ground
Ground
32
DIO A0
Digital I/O A0
8
VOUT 03
Analog Output 3
33
DIO B7
Digital I/O B7
9
Ground
Ground
34
DIO B6
Digital I/O B6
10
VOUT 04
Analog Output 4
35
DIO B5
Digital I/O B5
11
Ground
Ground
36
DIO B4
Digital I/OB4
12
VOUT 05
Analog Output 5
37
DIO B3
Digital I/O B3
13
Ground
Ground
38
DIO B2
Digital I/O B2
14
VOUT 06
Analog Output 6
39
DIO B1
Digital I/O B1
15
Ground
Ground
40
DIO B0
Digital I/O B0
16
VOUT 07
Analog Output 7
41
DIO C7
Digital I/O C7
17
VOUT 08
Analog Output 8
42
DIO C6
Digital I/O C6
18
VOUT 09
Analog Output 9
43
DIO C5
Digital I/O C5
19
VOUT 10
Analog Output 10
44
DIO C4
Digital I/O C4
20
VOUT 11
Analog Output 11
45
DIO C3
Digital I/O C3
21
VOUT 12
Analog Output 12
46
DIO C2
Digital I/O C2
22
VOUT 13
Analog Output 13
47
DIO C1
Digital I/O C1
23
VOUT 14
Analog Output 14
48
DIO C0
Digital I/O C0*
24
VOUT 15
Analog Output 15
49
V5_0
Protected +5.0 Volts
25
DIO A7
Digital I/O A7
50
Ground
Ground
* Pin 48 can also used as an external trigger for updating DAC channels. See External Trigger Update.
Installation
VCM-DAS-3 Reference Manual 11
Installation
HARDWARE ASSEMBLY
The VCM-DAS-3 uses pass-through PC/104 (ISA) connectors so that expansion modules can be
added to the top or bottom of the stack. PC/104 modules must not be positioned between the
CPU board and any PC/104-Plus (PCI) modules on the stack.
The entire assembly can sit on a table top or be secured to a base plate. When bolting the unit
down, make sure to secure all four standoffs to the mounting surface to prevent circuit board
flexing. Standoffs are secured to the top circuit board using four pan head screws. Standoffs and
screws are available as part number VL-HDW-101.
An extractor tool is available (part number VL-HDW-201) to separate the PC/104 modules from
the stack. Use caution when using the extractor tool not to damage any board components.
STACK ARRANGEMENT EXAMPLE
Figure 5. Stack Arrangement
BEE 24681111 2468 2468 13579135 13571357 1 v w.
VCM-DAS-3 Reference Manual 12
Configuration
Jumper Blocks
JUMPERS AS-SHIPPED CONFIGURATION
Figure 6. Jumper Block Locations
3 3
V1
V2
V3
1
3
5
7
9
11
13
15
1
3
5
7
1
3
5
7
2
4
6
8
2
4
6
8
2
4
6
8
10
12
14
16
Jumper Blocks
VCM-DAS-3 Reference Manual 13
JUMPER SUMMARY
Table 5: Jumper Summary
Jumper
Block
Description
As
Shipped
Page
V1[15-16]
Bit Mode Selector
In = 16-bit ISA Transactions
Out = 8-bit ISA Transactions
8-bit mode forces the VCM-DAS-3 to respond with 8-bit transactions. This mode
is required when using the board on an 8-bit bus. The 16-bit mode allows both 8
and 16-bit transactions.
In
15
V1[13-14]
Enhanced/Compatible Mode Selector
In = Enhanced Mode
Out = Compatible Mode
Enhanced mode provides extra DAC functions, which should operate properly in
applications designed for the Diamond Systems Ruby-MM board.
In
16
V1
[11-12] to
[1-2]
Base Address Selector A base address of 0x000 to 0x3F0 can be selected.
The last digit is always 0.
First Digit [11-12] 9-10]
0 In Out
1 Out In
2 Out In
3 Out Out
Second Digit [7-8] [5-6] [3-4] [1-2]
0 In In In In
1 In In In Out
2 In In Out In
3 In In Out Out
4 In Out In In
5 In Out In Out
6 In Out Out In
7 In Out Out Out
8 Out In In In
9 Out In In Out
A Out In Out In
B Out In Out Out
C Out Out In In
D Out Out In Out
E Out Out Out In
F Out Out Out Out
Out, Out,
In, In, In, In,
(0x300)
16
V2
A/D Channel 0-7 Span Range Selector
[7-8] [5-6] [3-4] [1-2]
0V to +5V In In In In
0V to +10V In In In Out
-5V to +5V In In Out In
-10V to +10V In In Out Out
-2.5V to +2.5V In Out In In
-2.5V to +7.5V In Out In Out
These jumpers set the initial power up span ranges for A/D channels 0-7.
In, In, In, In
(0V to +5V)
27
Base Address Configuration
VCM-DAS-3 Reference Manual 14
V3
A/D Channel 8-16 Span Range Selector
[7-8] [5-6] [3-4] [1-2]
0V to +5V In In In In
0V to +10V In In In Out
-5V to +5V In In Out In
-10V to +10V In In Out Out
-2.5V to +2.5V In Out In In
-2.5V to +7.5V In Out In Out
These jumpers set the initial power up span ranges for A/D channels 8-16.
In, In, In, In
(0V to +5V)
27
Base Address Configuration
As shipped, the VCM-DAS-3 is configured for a base address of 0x300. The card occupies up to
16 consecutive I/O addresses in enhanced mode (only eight I/O addresses in compatible mode).
Jumper block V1[11-12] through V1[1-2] is used set the base address.
The base address can be configured from 0x000 to 0x3F0 on any 10h address boundary. Figure 7
shows how to set the address selector jumpers for the appropriate upper and middle hex digits of
the three digit base address (for example, the “3” and “1” of base address 0x310).
D D DE DE III] an an III an an an an an an 7DD3 nu man u u u u u an u an man u u u u u an n u u an n u u u u an n u u nu an an
Bit Mode Configuration
VCM-DAS-3 Reference Manual 15
Figure 7. Base Address Jumpers
Bit Mode Configuration
The VCM-DAS-3 can operate using 8-bit or16-bit ISA transactions. For compatibility with 8-bit
ISA buses, you must set the VCM-DAS-3 to use 8-bit ISA transactions.
Jumper V1[15-16] selects the bit mode. When a jumper is present, the board will operate on
either 16-bit or 8-bit ISA bus. When the jumper is removed, the board is forced to perform only
8-bit ISA transactions. The default setting is jumper installed.
9 10
11 12
0
5
2
6
0
2
1
3
C
E
D
F
4
A
9
B
1
7
3
8
1 2
3 4
5 6
7 8
The lower digit is
always 0.
Upper
Digit
Middle
Digit
Lower
Digit
0x340 Example:
1 2
3 4
5 6
7 8
9 10
11 12
Enhanced Mode Configuration
VCM-DAS-3 Reference Manual 16
Enhanced Mode Configuration
Jumper V1[13-14] enables you to select between compatible or enhanced modes. A jumper
installed on V1[13-14] sets the VCM-DAS-3 to enhanced mode. When no jumper is installed, the
board operates in compatible mode. The default mode is enhanced.
In compatible mode, eight registers are decoded for use, including all the registers needed for
DAC and DIO operations and control. These registers are identical to those provided by the
Diamond Systems Ruby-MM, and enable full compatibility in applications designed with that
board. In this mode, analog output ranges are determined by jumper settings (in two banks of
eight registers) and are not software programmable.
Enhanced mode provides three additional registers for more specific control of DAC operations.
The ENH_CON register enables you to set spans for specific DAC channels, read DAC data and
spans, set DAC channels to sleep mode for power savings, and set and read the gain for all
channels.
Power-up Span Range Configuration
Jumper block V2 sets the initial span range for A/D channels 7-0. Jumper block V3 sets the
initial span range for A/D channels 15-8. (See Table 5 for a list of settings.) The span range can
be set differently for each 8-channel bank. Within each bank, all channels will have the same
initial span range; however, in enhanced mode, ranges can be set individually for each channel
via software.
Two unipolar output ranges (0V to 5V and 0V to 10V), and four bipolar ranges (±2.5V, ±5V,
±10V and -2.5V to 7.5V) are available.
VCM-DAS-3 Reference Manual 17
Registers
I/O Port Mapping
In enhanced mode, the VCM-DAS-3 operates occupies 16 ports in the I/O map. Eleven ports are
mapped to functional registers, and the remaining five ports are decoded by the board and cannot
be used by other PC/104 modules.
Table 6: Enhanced Mode I/O Port Addresses
Write Register
Read Register
I/O Port Address
As Shipped
Address
PLDVER
Base Address + F
0x30F
Base Address + E
0x30E
Base Address + D
0x30D
Base Address + C
0x30C
Base Address + B
0x30B
ENCTRL
ENCTRL
Base Address + A
0x30A
ENDATHI
ENDATHI
Base Address + 9
0x309
ENDATLO
ENDATLO
Base Address + 8
0x308
DIOCTRL
DIOCTRL
Base Address + 7
0x307
DIOC
DIOC
Base Address + 6
0x306
DIOB
DIOB
Base Address + 5
0x305
DIOA
DIOA
Base Address + 4
0x304
EXTRIG
EXTRIG
Base Address + 3
0x303
DACSEL
Base Address + 2
0x302
DACHI
DACALL1
Base Address + 1
0x301
DACLO
DACALL0
Base Address + 0
0x300
In compatible mode, the VCM-DAS-3 operates occupies eight ports in the I/O map, all of which
are functional.
4 4
I/O Port Mapping
VCM-DAS-3 Reference Manual 18
Table 7: Compatible Mode I/O Port Addresses
Write Register
Read Register
I/O Port Address
As Shipped
Address
DIOCTRL
DIOCTRL
Base Address + 7
0x307
DIOC
DIOC
Base Address + 6
0x306
DIOB
DIOB
Base Address + 5
0x305
DIOA
DIOA
Base Address + 4
0x304
EXTRIG
EXTRIG
Base Address + 3
0x303
DACSEL
Base Address + 2
0x302
DACHI
DACALL1
Base Address + 1
0x301
DACLO
DACALL0
Base Address + 0
0x300
I/O PORT REGISTER FUNCTIONS
The following table lists the functions assigned to each read and write I/O port register.
Table 8: Register Functions
Write Register
Description
Page
ENCTRL
Enhanced control
19
ENDATHI
Enhanced Data MSB
20
ENDATLO
Enhanced Data LSB
20
DIOCTRL
Digital I/O control register
21
DIOC
Digital I/O port C data
23
DIOB
Digital I/O port B data
23
DIOA
Digital I/O port A data
23
EXTRIG
External trigger enable
24
DACSEL
DAC channel register
25
DACHI
Analog output most significant data byte (MSB).
26
DACLO
Analog output least significant data byte (LSB).
26
Read Register
Description
Page
ENCTRL
Enhanced control
19
ENDATHI
Enhanced Data MSB
20
ENDATLO
Enhanced Data LSB
20
DIOCTRL
Digital I/O control register
21
DIOC
Digital I/O port C data
22
DIOB
Digital I/O port B data
22
DIOA
Digital I/O port A data
22
EXTRIG
External trigger enable
24
DACALL1
Update all DACs simultaneously
26
DACALL0
Update all DACs simultaneously
26
Enhanced Mode Registers
VCM-DAS-3 Reference Manual 19
Enhanced Mode Registers
Setting the VCM-DAS-3 to enhanced mode enables three additional functional registers. To
enable enhanced mode, install a jumper on pins V1[13-14].
ENHANCED CONTROL REGISTER
ENCTRL (Write) 030Ah
7
6
5
4
3
2
1
0
CTRL3
CTRL2
CTRL1
CTRL0
SEL3
SEL2
SEL1
SEL0
Table 9: Register Bit Assignments
Bit
Mnemonic
Description
7-4
CTRL
Enhanced DAC Control These bits select operations to be performed on
specific DAC channels.
CTRL3 CTRL2 CTRL1 CTRL0 Function
0 0 0 0 Set Span: 0V to +5V
0 0 0 1 Set Span: 0V to +10V
0 0 1 0 Set Span: -5V to +5V
0 0 1 1 Set Span: -10V to +10V
0 1 0 0 Set Span: -2.5V to +2.5V
0 1 0 1 Set Span: -2.5V to +7.5V
0 1 1 0 (Reserved. Do not use.)
0 1 1 1 (Reserved. Do not use.)
1 0 0 0 Read DAC
1 0 0 1 Read Span
1 0 1 0 Load DAC (LDAC)
1 0 1 1 DAC Sleep
1 1 0 0 (Reserved. Do not use.)
1 1 0 1 (Reserved. Do not use.)
1 1 1 0 Set Gain
1 1 1 1 Read Gain
3-0
SEL
Channel Selection These bits select the DAC channel for the operation.
SEL3 SEL2 SEL1 SEL0 Channel
0 0 0 0 0
0 0 0 1 1
0 0 1 0 2
0 0 1 1 3
0 1 0 0 4
0 1 0 1 5
0 1 1 0 6
0 1 1 1 7
1 0 0 0 8
1 0 0 1 9
1 0 1 0 10
1 0 1 1 11
1 1 0 0 12
1 1 0 1 13
1 1 1 0 14
1 1 1 1 15
Enhanced Mode Registers
VCM-DAS-3 Reference Manual 20
ENCTRL (Read) 030Ah
7
6
5
4
3
2
1
0
READY
Table 10: Register Bit Assignments
Bit
Mnemonic
Description
7-1
Enhanced DAC Control
0
Ready
Ready Factory use only.
0 = SPI transaction in progress
1 = SPI transaction complete
The internal logic of the SPI state machine is much faster than the ISA bus
speed, which limits the usefulness of his bit for anything other than factory
debugging of the design.
ENHANCED MODE DATA REGISTERS
ENDATHI MSB (Read) 0309h
7
6
5
4
3
2
1
0
D15
D14
D13
D12
D11
D10
D9
D8
ENDATLO LSB (Read/Write) 0308h
7
6
5
4
3
2
1
0
D7
D6
D5
D4
D3
D2
D1
D0
The data format of these registers depends on the operation executed in the ENCTRL register.
See the sections listed below for information on data formats for specific operations.
Operation
CTRL Code
(ENCTRL)
Page
Read DAC
08h
35
Read Span
09h
35
Set Gain
0Eh
34
Read Gain
0Fh
34
Digital I/O Control Register
VCM-DAS-3 Reference Manual 21
Digital I/O Control Register
DIOCTRL (Read/Write) 0307h
7
6
5
4
3
2
1
0
DIRA
DIRCHI
DIRB
DIRCLO
Table 11: DIOCTRL Bit Assignments
Bit
Mnemonic
Description
7-5
Unused. These bits have no function.
4
DIRA
DIO Port A Direction These bits control the direction of DIO port A (A7-A0).
0 = Output
1 = Input
3
DIRCHI
DIO Port C MSB Direction These bits control the direction of the upper half of
DIO port C (C7-C4).
0 = Output
1 = Input
2
Unused. This bit has no function.
1
DIRB
DIO Port B Direction These bits control the direction of DIO port B (B7-B0).
0 = Output
1 = Input
0
DIRCLO
DIO Port C LSB Direction These bits control the direction of the lower half of
DIO port C (C3-C0).
0 = Output
1 = Input
Digital I/O Data Registers
VCM-DAS-3 Reference Manual 22
Digital I/O Data Registers
DIGITAL INPUT REGISTERS
DIOA (Read) 0304h
D7
D6
D5
D4
D3
D2
D1
D0
DIO A7
DIO A6
DIO A5
DIO A4
DIO A3
DIO A2
DIO A1
DIO A0
DIOB (Read) 0305h
D7
D6
D5
D4
D3
D2
D1
D0
DIO B7
DIO B6
DIO B5
DIO B4
DIO B3
DIO B2
DIO B1
DIO B0
DIOC (Read) 0306h
D7
D6
D5
D4
D3
D2
D1
D0
DIO C7
DIO C6
DIO C5
DIO C4
DIO C3
DIO C2
DIO C1
DIO C0
Table 12: Digital Input Data Bit Assignments
Bit
Mnemonic
Description
7-0
DIO A7-A0
DIO B7-B0
DIO C7-C0
Digital Input Data Data read from these registers returns the current input
state of the digital port signals on connectors J1 and J2. Data is not inverted.
When a signal line is high, the bit reads as 1; when a signal line is low, the bit
reads as 0.
To operate a port in input mode, you must first set the direction of the port to
input by setting the appropriate bit in the DIOCTRL register. If a port is operated
in output mode, the registers can be used to read back the logic state of the
output lines. Normally, the data read would be the same as the data written to
the output registers; however, if an output line is stuck high or shorted to ground,
the fault will be reflected in the feedback data.
Digital I/O Data Registers
VCM-DAS-3 Reference Manual 23
DIGITAL OUTPUT REGISTERS
DIOC (Write) 0306h
D7
D6
D5
D4
D3
D2
D1
D0
DIO C7
DIO C6
DIO C5
DIO C4
DIO C3
DIO C2
DIO C1
DIO C0
DIOB (Write) 0305h
D7
D6
D5
D4
D3
D2
D1
D0
DIO B7
DIO B6
DIO B5
DIO B4
DIO B3
DIO B2
DIO B1
DIO B0
DIOA (Write) 0304h
D7
D6
D5
D4
D3
D2
D1
D0
DIO A7
DIO A6
DIO A5
DIO A4
DIO A3
DIO A2
DIO A1
DIO A0
Table 13: Digital Output Data Bit Assignments
Bit
Mnemonic
Description
D7-D0
DIO A7-A0
DIO B7-B0
DIO C7-C0
Digital Output Data Data written to these registers is driven onto the digital
port signals on connectors J1 and J2. Data is not inverted. When a bit is set to
1, the signal line is driven high; when a bit is reset to 0, the signal line is driven
low.
To operate a port in output mode, you must first set the direction of the port to
output by clearing the appropriate bit in the DIOCTRL register.
External Trigger Enable Register
VCM-DAS-3 Reference Manual 24
External Trigger Enable Register
EXTRIG (Read/Write) 0303h
7
6
5
4
3
2
1
0
TRIGEN
Table 14: EXTRIG Bit Assignments
Bit
Mnemonic
Description
7-1
Unused. These bits have no function.
0
TRIGEN
Trigger Enable When the external trigger is enabled, digital I/O line C0 will
update all DACs simultaneously when it is brought low. This can be done either
by an external signal, when C0 is in input mode, or in software, when C0 is in
output mode. If using an external trigger, make sure that the lower half of Port C
is in input mode.
1 = Enable
0 = Disable
Analog Output Data Registers
VCM-DAS-3 Reference Manual 25
Analog Output Data Registers
DAC CHANNEL SELECT REGISTER
DACSEL (Write) 0302h
7
6
5
4
3
2
1
0
SEL3
SEL2
SEL1
SEL0
Table 15: DACSEL Bit Assignments
Bit
Mnemonic
Description
7-4
Unused. These bits have no function.
3-0
SEL
Channel Selection These bits select the DAC channel upon which digital
output functions will be performed.
SEL3 SEL2 SEL1 SEL0 Selected Channel
0 0 0 0 0
0 0 0 1 1
0 0 1 0 2
0 0 1 1 3
0 1 0 0 4
0 1 0 1 5
0 1 1 0 6
0 1 1 1 7
1 0 0 0 8
1 0 0 1 9
1 0 1 0 10
1 0 1 1 11
1 1 0 0 12
1 1 0 1 13
1 1 1 0 14
1 1 1 1 15
Analog Output Data Registers
VCM-DAS-3 Reference Manual 26
DAC WRITE REGISTERS
DACHI (Write) 0301h
7
6
5
4
3
2
1
0
DA11
DA10
DA9
DA8
DACLO (Write) 0300h
7
6
5
4
3
2
1
0
DA7
DA6
DA5
DA4
DA3
DA4
DA1
DA0
Table 16: DACHI Bit Assignments
Bit
Mnemonic
Description
7-4
Unused. These bits have no function.
3-0
DACHI
Analog Output Data MSB Digital-to-analog data bits DA11-DA8. DA11 is
the most significant bit. This register is used with the DACLO register to form
the 12-bit analog output value.
Table 17: DACLO Bit Assignments
Bit
Mnemonic
Description
7-0
DACLO
Analog Output DATA LSB Digital-to-analog data bits DA7-DA0. DA0 is
the least significant bit. This register is used with the DACHI register to form
the 12-bit analog output value.
DAC READ REGISTERS
DACALL1 (Read) 0301h
7
6
5
4
3
2
1
0
DA11
DA10
DA9
DA8
DACALL0 (Read) 0300h
7
6
5
4
3
2
1
0
DA7
DA6
DA5
DA4
DA3
DA4
DA1
DA0
Reading from these locations updates all DACs to the values written to them. Only DACs with
new data written to them will change. The remaining channels will retain their current values.
VCM-DAS-3 Reference Manual 27
Analog Output
Analog Output Ranges and Resolution
VCM-DAS-3 provides six different analog output ranges (shown in Table 18), including four
bipolar ranges and two unipolar ranges. One of the bipolar ranges (-2.5 to +7.5V) is
asymmetrical. Power-up ranges are determined by jumper settings (see Power-up Span Range
Configuration). Ranges for individual channels can be set by software using the Set Span
command, available in enhanced mode.
The resolution for any output range is equal to the maximum possible range of output voltages
divided by the maximum number of possible steps. For a 12-bit D/A converter, the maximum
number of steps is 4096. The actual output codes range from 0 to 4095, which is the full range of
possible 12-bit binary numbers. (See Analog Output Data Representation.)
The table below shows the analog output ranges and resolutions available on the VCM-DAS-3.
Negative full scale refers to the output voltage for a code of 0, and positive full scale refers to the
output voltage for a code of 4095.
Table 18: Analog Output Ranges and Resolution
Full-Scale
Voltage
Bipolar or
Unipolar
Range
Name
Negative
Full Scale
Positive
Full Scale
Resolution
(1 LSB)
10V
Bipolar
±10V
-10V
+9.9951V
4.88mV
5V
Bipolar
±5V
-5V
+4.9963V
2.44mV
2.5V
Bipolar
±2.5V
-2.5V
+2.4988V
1.22mV
7.5V
Bipolar
-2.5 to +7.5V
-2.5V
+7.4963V
2.44mV
10V
Unipolar
0-10V
0V
+9.9976V
2.44mV
5V
Unipolar
0-5V
0V
+4.9988V
1.22mV
SETTING A SPAN RANGE
Power-up span ranges are determined for blocks of channels by jumper settings (see Power-up
Span Range Configuration); however, in enhanced mode, you can set the span range for any
individual channel. To perform a Set Span operation:
1. Write the appropriate Set Span code (see Enhanced Control Register) to the CTRL field
of the ENCTRL register at I/O port 0x30A, combined with the channel number in the
SEL bits of the same register.
2. Perform an LDAC operation by writing Ah to the CTRL field of the ENCTRL register,
combined with the channel number in the SEL field of the same register.
5 5
Analog Output Data Representation
VCM-DAS-3 Reference Manual 28
Analog Output Data Representation
Two different digital coding schemes are used for analog output operations.
For unipolar output ranges (positive voltages only), straight binary coding is used.
For bipolar output ranges (both positive and negative voltages), offset binary coding is
used.
STRAIGHT BINARY CODING
The formulas for calculating analog or straight binary digital values are given by:
Where:
Analog = Applied voltage
Digital = A/D conversion data
Step = 0.00244140625 for 0-10V range
0.00122070313 for 0-5V range
0.0006103515625 for 0-2.5V range
Table 19: Straight Binary Data Format
0-2.5V
Range
0-5V
Range
0-10V
Range
Hex
Decimal
Comment
+2.5000
+5.0000
+10.0000
Out of range
+2.4993
+4.9987
+9.9975
FFFh
4095
Maximum positive voltage
+1.2500
+2.5000
+5.0000
800h
2048
Positive half scale
+0.6250
+1.2500
+2.5000
400h
1024
Positive quarter scale
+0.00061
+0.00122
+0.00244
001h
1
Positive 1 LSB
0.0000
0.0000
0.0000
000h
0
Zero (ground output)
Digital =
Analog
Step
Analog = Step x Digital
Analog Output Data Representation
VCM-DAS-3 Reference Manual 29
OFFSET BINARY CODING
The formulas for calculating analog or straight binary digital values are given by:
Where:
Analog = Applied voltage
Digital = A/D conversion data
Offset1 = 2048 for symmetrical ranges
1024 for asymmetrical range
Step = 0.00122070313 for ±2.5V range
0.00244140625 for ±5V and -2.5 to +7.5 ranges
0.0048828125 for ±10V range
Offset2 = 2.5 for ±2.5V and -2.5 to +7.5 ranges
5 for ±5V
10 for ±10V range
Table 20: Offset Binary Data Format Symmetrical Ranges
±2.5V
Output
Voltage
±5V
Output
Voltage
±10V
Output
Voltage
Hex
Decimal
Comment
+2.5000
+5.0000
+10.0000
Out of range
+2.4987
+4.9975
+9.9951
FFFh
4095
Maximum positive voltage
+1.2500
+2.5000
+5.0000
C00h
3072
Positive half scale
+0.6250
+1.2500
+2.5000
A00h
2560
Positive quarter scale
+0.00122
+0.00244
+0.00488
801h
2049
Positive 1 LSB
0.0000
0.0000
0.0000
800h
2048
Zero (ground voltage)
-0.00122
-0.00244
-0.00488
7FFh
2047
Negative 1 LSB
-0.6250
-1.2500
-2.5000
600h
1536
Negative quarter scale
-1.2500
-2.5000
-5.0000
400h
1024
Negative half scale
-2.5000
-5.0000
-10.0000
000h
0
Maximum negative voltage
Digital =
Analog = (Step x Digital) - Offset2
+ Offset1
Analog
Step
Analog Output Data Representation
VCM-DAS-3 Reference Manual 30
Table 21: Offset Binary Data Format Asymmetrical Range
-2.5 to +7.5
Output
Voltage
Hex
Decimal
Comment
+7.5000
Out of range
+7.4975
FFFh
4095
Maximum positive voltage
+3.7500
A00h
2560
Positive half scale
+1.8750
700h
1792
Positive quarter scale
+0.00244
401h
1025
Positive 1 LSB
0.0000
400h
1024
Zero (ground voltage)
-0.00244
3FFh
1023
Negative 1 LSB
-0.6250
300h
768
Negative quarter scale
-1.2500
200h
512
Negative half scale
-2.5000
000h
0
Maximum negative voltage
Analog Output Programming
VCM-DAS-3 Reference Manual 31
Analog Output Programming
Analog output voltages can be programmed either directly or with the use of a driver. This
section describes how to modify analog output voltages directly.
VCM-DAS-3 analog outputs have a resolution of 12 bits. Data is written to the board in 8-bit
bytes, so two bytes must be used to write a single analog output value. These bytes are referred to
as the least significant byte (LSB) and the most significant byte (MSB).
When modifying analog outputs, one or multiple channels can be updated simultaneously. For
this reason, the update operation is separate from the data write operation.
To change an analog output on one or more channels:
1. Write the channel number to the DACSEL register at I/O port 0x302.
2. Write the LSB to the DACLO register at I/O port 0x300.
3. Write the MSB to the DACHI register at I/O port 0x301.
4. Repeat steps 1-3 for each channel to be changed.
5. Finally, update all channels simultaneously by reading the DACLO register.
EXTERNAL TRIGGER UPDATE
An external trigger is enabled by setting the TRIGEN bit in the EXTRIG register at I/O port
0x303. When the external trigger is enabled, digital I/O line C0 will update all DACs
simultaneously when it is brought low. This can be done either by an external signal, when C0 is
in input mode, or in software, when C0 is in output mode. If using an external trigger, make sure
that the lower half of Port C is in input mode.
When the trigger signal is low, DACs are updated as soon as new data is written to them. When
the trigger signal is high, the DAC voltage outputs remain fixed, unless updated in software.
LOAD DAC OPERATION
The Load DAC (LDAC) operation provides a method for updating a single DAC channel. To
perform the LDAC operation, write Ah to the CTRL field of the ENCTRL register at I/O port
0x30A, combined with the channel number in the SEL field of the same register.
To change an analog output a single channel using the LDAC operation:
1. Write the channel number to the DACSEL register at I/O port 0x302.
2. Write the LSB to the DACLO register at I/O port 0x300.
3. Write the MSB to the DACHI register at I/O port 0x301.
4. Perform the LDAC operation for the selected channel.
Analog Output Code Example
VCM-DAS-3 Reference Manual 32
Analog Output Code Example
The following Visual BASIC code illustrates how to operate the analog output feature of the
VCM-DAS-3.
FUNCTION LIB_das3aout (BYVAL channel, BYVAL range, BYVAL voltage)
'
'Description: This function performs an
' analog output operation to the
' specified channel.
'
'Entry: channel: analog output channel (0 to 15)
' range: 0=5V, 1=10V, 2=+/-5V, 3=+/-10V
' 4=2.5V, 5=-2.5V/+7.5V
' voltage: analog output voltage (within range)
'
'Returns: 0 if no errors
' 1 if timeout occurs
'
'Examples: 'Output +5.000V on channel 0
' x = LIB_das3aout (0,1,5.000)
'
' 'Output -7.500V on channel 1
' x = LIB_das3aou (1, 3, -7.500)
'
'Enhanced Control Register (BASE + 0xA)
' D7 D6 D5 D5 D3 D2 D1 D0
' EC3 EC2 EC1 EC0 ---DAC CHANNEL---
' =====================================
' 0V to +5V 0 0 0 0
' 0V to +10V 0 0 0 1
' -5V to +5V 0 0 1 0
' -10V to +10V 0 0 1 1
'-2.5V to +2.5V 0 1 0 0
'-2.5V to +7.5V 0 1 0 1
DIM value AS INTEGER
DIM hidac AS INTEGER
DIM lodac AS INTEGER
DIM done AS INTEGER
DIM y AS INTEGER
DIM x AS INTEGER
DIM bipolar AS INTEGER
DIM fullscale AS SINGLE
SELECT CASE range
CASE 0 '+5V
bipolar = 0
fullscale = 5
CASE 1 '+10V
bipolar = 0
fullscale = 10
CASE 2 '+/-5V
bipolar = 1
fullscale = 5
CASE 3 '+/-10V
Analog Output Code Example
VCM-DAS-3 Reference Manual 33
bipolar = 1
fullscale = 10
CASE 4 '+/-2.5V
bipolar = 1
fullscale = 2.5
CASE 5 '+7.5/-2.5V
bipolar = 2
fullscale = 7.5
END SELECT
IF bipolar = 1 THEN
'offset binary coding (symetrical ratio)
value = INT((voltage / fullscale) * 2048 + 2048)
ELSEIF bipolar = 2 THEN 'offset binary coding (asymetrical ratio)
value = INT((voltage / fullscale) * 3072 + 1024)
ELSE 'Unipolar
'straight binary coding
value = INT((voltage / fullscale) * 4096)
END IF
'Limit excursion
IF value > 4095 THEN
value = 4095
END IF
'Separate low byte from high nibble
lodac = value AND &HFF
hidac = (value AND &HF00) / 256
'Set selected DAC channel to the desired range
'(ENHANCED MODE REGISTER)
OUT BASE + &HA, ((range * 16) + channel)
'Set selected DAC channel to desired voltage
OUT BASE, lodac
OUT BASE + 2, channel
OUT BASE + 1, hidac
'A single read updates all outputs
x = INP(BASE)
'Wait for DONE or timeout before returning
done = 0
y = 0
WHILE NOT done
y = y + 1
IF y < 2000 THEN 'timeout
done = INP(BASE + &HA) AND &H01 '(ENHANCED MODE REGISTER)
ELSE
LIB_das3aout = 1
EXIT FUNCTION
END IF
WEND
LIB_das3aout = 0
END FUNCTION
Calibration
VCM-DAS-3 Reference Manual 34
Calibration
Calibration, if desired, is accomplished by mathematical transformation in software. Gain for the
board (not individual channels) can be adjusted using the ENCTRL register. Offset adjustments
are not currently implemented on the board.
An SPI transaction to the gain pot will take less than 10 us. However, the Gain pot takes up to 20
ms to update its EEPROM when written to. During calibration, you need to wait 2 ms after the
write command before measuring the voltage of the DAC output.
SETTING THE GAIN
The range of gain adjustment is 24 mV. The gain is encoded using the eight bits of the
ENDATLO register, so each step equals 0.094 mV. To perform the Set Gain command, write
E0h to the ENCTRL register at I/O port 0x30A, and then write the gain value to the ENDATLO
register at I/O port 0x308. The following procedure is recommended for setting the gain:
1. Select channel 0 by writing 0h to the DACSEL register at I/O port 0x302.
2. Output the code for 0V by writing 0h to both the DACHI and DACLO registers.
3. Using high-precision volt meter (VOM), read the voltage on channel 0. The voltage read
is the offset.
4. Output the code for known voltage minus the offset to channel 0.
5. Using the VOM, read voltage on channel 0. The difference between the VOM reading
and the known voltage applied in step 4 is the gain error.
6. Adjust gain pot up or down to reduce the gain error to the lowest possible amount.
Note that there is no adjustment for offset error. You must accommodate for offset with software.
The gain value you set is non-volatile.
READING THE GAIN
To perform the Read Gain operation, write F0h to the ENCTRL register at I/O port 0x30A, and
then read the value of the ENDATLO register at I/O port 0x308.
Enhanced Mode Operations
VCM-DAS-3 Reference Manual 35
Enhanced Mode Operations
The VCM-DAS-3 must be in enhanced mode to perform enhanced mode operations.
READING DAC DATA
Reading a DAC using the Read DAC operation does not cause the DAC to be updated, as reading
the DACALL0 register does. Performing a Read DAC operation loads the DAC voltage code in
the ENDATHI and ENDATLO registers. To read the voltage of a DAC:
1. Perform a Read DAC operation by writing 8h to the CTRL field of the ENCTRL register
at I/O port 0x30A, combined with the channel number in the SEL field of the same
register.
2. Read the ENDATHI register and then the ENDATLO register. The 12 bits of the output
voltage code are offset toward the MSB, as shown below.
ENDATHI MSB (Read) 0309h
7
6
5
4
3
2
1
0
D11
D10
D9
D8
D7
D6
D5
D4
ENDATLO LSB (Read) 0308h
7
6
5
4
3
2
1
0
D3
D2
D1
D0
0
0
0
0
READING THE SPAN OF A CHANNEL
To read the span of a channel:
1. Perform a Read Span operation by writing 9h to the CTRL field of the ENCTRL register
at I/O port 0x30A, combined with the channel number in the SEL field of the same
register.
2. Read the span code from bits 3-0 of the ENDATLO register at I/O port 0x308, as shown
below.
ENDATLO LSB (Read) 0308h
7
6
5
4
3
2
1
0
D3
D2
D1
D0
Enhanced Mode Operations
VCM-DAS-3 Reference Manual 36
SETTING A CHANNEL TO SLEEP MODE
To set a DAC to sleep mode, perform a Sleep DAC operation by writing Bh to the CTRL field of
the ENCTRL register at I/O port 0x30A, combined with the channel number in the SEL field of
the same register. The channel remains in sleep mode until a voltage output code is written to it.
READING THE SLEEP STATUS OF A CHANNEL
To read the sleep status of a channel:
1. Perform a Read Span operation by writing 9h to the CTRL field of the ENCTRL register
at I/O port 0x30A, combined with the channel number in the SEL field of the same
register.
2. Read the SLEEPSTAT bit (bit 4) of the ENDATLO register at I/O port 0x308, as shown
below. A value of 0 = awake. A value of 1 = sleep mode.
ENDATLO LSB (Read) 0308h
7
6
5
4
3
2
1
0
SLEEPSTAT
VCM-DAS-3 Reference Manual 37
Digital I/O
Signal Direction
The 24 digital I/O port signals on the VCM-DAS-3 can be configured as inputs or outputs, in
groups of eight or, in the case of port DIOC, in groups of four. Signal direction is set by
manipulating the bits in the DIOCTRL register. The logic level on any digital I/O channel can be
set by writing a 1 or 0 to the appropriate bit. The digital I/O interface of the VCM-DAS-3 are
82C55 Mode 0 compatibly only.
Signal Polarity
All digital I/O circuits on the VCM-DAS-3 are non-inverted, true logic. A high logic level is
represented by a 1 in the digital I/O data registers, and a low logic level is represented by a 0.
Since Opto 22 modules invert the logic sense of signals passed through them, the register-to-
module interface is negative logic. The resulting data interface levels between the VCM-DAS-3
and I/O rack modules are shown below.
Data
Written
I/O
Pin
Output
Modules
Input
Modules
I/O
Pin
Data
Read
0
(Low)
Power On
Voltage Present
(Low)
0
1
(High)
Power Off
Voltage Absent
(High)
1
Digital Input
The logic state of the digital input channels can be read at any time by reading the DIOA, DIOB,
or DIOC registers. Simply choose the correct register and read it as an 8-bit quantity.
Digital Output
The logic state of any digital output channel can be manipulated at any time by writing to the
DIOA, DIOB, or DIOC registers. Simply choose the correct register and write the digital value as
an 8-bit quantity.
6 6
LTC2704 Datasheet PC/ 104 Consortium VersaLogic Comoralion Microsoft Press Powell’s Books
VCM-DAS-3 Reference Manual 38
References
DAC Controller LTC2704 Datasheet
Linear Technology LTC2704
PC/104 Specification PC/104 Consortium
PC/104 Resource Guide
PC/104-Plus Specification VersaLogic Corporation
PC/104 Resource Guide
General PC Documentation Microsoft Press
The Programmer’s
PC Sourcebook
General PC Documentation Powell’s Books
The Undocumented PC
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