Measurement Computing PCM-DAC08 - Manual (Page 18)

7 I/O ADDRESS MAP & REGISTER FUNCTIONS
A base address register controls the beginning, or 'Base Address' of the I/O addresses
occupied by the control registers of the PCM-DAC08. In all, 5 addresses are occu-
pied. Once the CSS is installed, the base address may be modified by runing the
InstaCal program. The base address assigned by InstaCal is stored in the CB.CBG file
and read by the CSS installed in your computer. Please read about installing and
using InstaCal.
7.1 CONTROL REGISTERS
Once CSS is installed and a base address has been established, the PCM-DAC08 may
be controlled by writing to and reading from the control registers. While it is possible
to write you own control routines for the PCM-DAC08, routines have been written
and are available in UniversalLibrary for DOS and Windows programming languages.
NOTE ON REGISTER PROGRAMMING SUPPORT
While the complete register map is explained here, only very limited support for
assembly language or direct register programming is available. If you have a question
regarding direct register programming, you must FAX it. The engineering department
does not accept techinical support calls but will answer faxes.
The ASSEMBLY source code to the Universal Library is not available. Information
on writing interrupt service routines and other programming tasks related to the per-
sonal computer or PCMCIA slots is not available. We support the use of the PCM-
DAC08 through high level languages using UniversalLibrary and the example pro-
grams provided. If there is an extension to the UniversalLibrary that would be of use
to you, please FAX your request to the attention of Software Engineering.
7.2 CONTROL REGISTERS ARE 8 BITS
All I/O access may be performed as bytes or words. Eight bit addressing is controlled
by the CSS, which is currently set for 8 bit addressing as supplied by
ComputerBoards. The registers are presented in 8 bit format here.
BASE + 0 - DAC0 LSB Data Register
Any read to this register will trigger an D/A conversion. This is a good method of
starting conversions from software or time of day clock control.
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