DAQ-1212ETM User's Manual
Introduction The DAQ-1212ETM is unique in its complement of 8 channels of both input and output,
analog and digital, enabling multichannel DSP operations on a single plug-in board to the
PC. Its features were designed for maximum value for use in embedded control systems,
with digital I/O included on board for support of the system function. Analog inputs
Analog outputs
TTL inputs
TTL outputs
Other
A Note Regarding Accuracy Please note that the DAQ-1212E has been designed
to emphasize low noise operation, ease of use, reliability and reduced cost.
The overall accuracy of any measurement
system is best determined by actual measurements on-site that include the errors
induced by cabling and any external circuits involved. The DAQ-1212E provides a stable
and repeatable result that can be calibrated to the accuracy of an external reference with a
simple maintenance program. Installing the DAQ-1212E Before installing the DAQ-1212E into an ISA bus socket, the address switch setting
should be confirmed and changed if necessary. The switch sets the base address of an
8-address space required for direct communication with the various registers and functions
of the DAQ-1212E. ISA address bits A3 through A9 are compared with the upper seven switches of
switch S1. An OFF switch setting corresponds with a logical '1' and an ON setting with a
logical '0'. Switch 1 must always be set to ON. Switches 2-8 are set to match address 320
(hex) at time of manufacture, but may be changed as desired to any unused address.
When the address setting is acceptable, the DAQ-1212E may be installed in any
spare ISA bus slot. Several interface and control programs are provided for the
DAQ-1212E, but any program capable of reading and writing word transfers to/from the
ISA-bus (16-bits) can be used for communications. It is only necessary to
follow the protocol
described below. Internal Addressing The listed addresses allow communication with the DAQ-1212E control and data
registers.
Note: All channel numbers are in the range of 0-7. A/D Conversion To perform an A/D conversion on a selected channel, simply
write the channel number
to the base address, then read the converted response at the same address. Because
of a pipeline feature in the DAQ-1212E design, there is a two-sample delay when reading
the converted data. This delay must be taken into account in the design of interface control
programs. When sequentially sampling all channels, for example, the data for channel 3
would be read back after the command for channel 5 is sent. To read a single channel,
write the channel number once and read three times, discarding the first two readings. The DAQ-1212E performs the conversion in 2 microseconds, and the pipeline may
be read with no wait states, so the maximum delay for a single reading is 2 microseconds
plus the length of time required by your software to make two readings. An assembly language
program could perform the entire process in less than 3 microseconds, making the
DAQ-1212E the fastest economy-priced board on the market. In applications that require several high speed measurements, there is no significant
delay caused by the pipelining. Simply assign storage with the two-sample delay in
mind. D/A Conversion Analog output control is slightly more complex than the analog input method. The
12-bit output value must be divided into two words. The lower 8-bits are written to the base
address+2 and the high 4-bits to the base address+6. In both cases, the channel number
is contained in the upper 4-bits of the 16-bit word written to the DAQ-1212E. In the BASIC
language, the formatting can be performed in the following manner:
The LSB is then written to the base address+2, the MSB is written to the base
address+6 and the entire 12-bit data is transferred to the D/A converters by reading the
base address+2. For example, to write the hex value 38E to channel 6, we would proceed as follows: The channel number is passed in the upper 4 bits of the control word, so it becomes
6000 (hex). Then we separate the msb (3) and the lsb (8E) and combine each one with the
channel number. Thus, the word written to the lsb at base address+2 is 608E and the word
written to the msb at base address+6 is 6003. We then read base address+2 to complete
the transfer. I/O Addressing Control and communication with the digital inputs and outputs is the most direct of
all. Simply write the output data to the base address+1 and read the input data from the
same address. In BASIC, we have:
Configuration There are no software-configurable controls on the DAQ-1212E
board. Various in-put and output voltage ranges and gains are available on
special order, but are fixed by resistor
selection and cannot be changed by the operating program. Applications that
require run-time control of these functions are served by the DAQ-1212C. Interrupts The DAQ-1212E does not support interrupts. Applications that require interrupt
support are served by the DAQ-1212C. DMA Access The DAQ-1212E does not support Direct Memory Access. Future versions of the
DAQ-1212 family will provide this and other functions, as requested. Connector Pin Definitions There is a single DB-37 connector provided for access to all functions of the
DAQ-1212E. The definitions are identical to those for the DAQ-1212A,B, and C.
Support Products Several support products for test and maintenance of the DAQ-1212E are available
from the manufacturer. These include a loop-back test board that uses the analog outputs
to test and calibrate the analog inputs (with a calibration-quality voltmeter), and ties the
digital outputs to the digital inputs, as well. Software The following programs are included with the DAQ-1212E at no cost. They are primarily
intended for use in test and evaluation, as well as to provide examples of tested
communications techniques. Documented source code is included for all programs. DAQ1212E.qlb is a QuickBASIC "quick library" file that provides the ability to read
and write 16-bit integers to the ISA bus from QuickBASIC programs. DAQ1212E.bas is a test program that allows the user to access all functions of the
DAQ-1212E under manual control. DAQ12AT.bas is an acceptance test program that provides the necessary setups
to test and calibrate all functions of the DAQ-1212E. It uses the loop-back test board or
equivalent connection to connect the analog and digital outputs to their respective inputs. Through use of this program, it is possible to test the range, linearity and noise level
of the analog inputs, to clear all analog outputs to maximum negative or half scale, to set
individual output values, and to read individual input values. This program is supplied in text form to serve as a maintenance tool as well as to
provide a guide for user-written programs. The necessary library is included as a ".qlb" file
as well as in assembly source code. The assembly code appears as "wordin.asm" and
"wordout.asm". A "C" language library is in preparation to provide basic functions such as
"read_A2D()", "write_D2A()", "init_D2A()" etc. Please contact the factory regarding
availability. Copyright © Diva Automation
|