5 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 PC-CARD-DAC08. Sixteen addresses are
allocated to the PC-CARD, however, only 5 addresses are actually used. The base
address assigned by CSS is stored in the CB.CBG file by InstaCal.
After CSS is installed and a base address has been established, the PC-CARD-DAC08
is controlled by writing to and reading from the control registers. While it is possible
to write your own control routines, routines have been written and are available in
Universal library for DOS and Windows programming languages. We support the use
of the PC-CARD-DAC08 through high level languages using Universal Library.
All I/O access can be performed as bytes or words. Eight-bit addressing is controlled
by the CSS, which is currently set for 8-bit addressing. The registers are presented in
8-bit format here.
BASE + 0 - DAC0 LSB Data Register
D/A0
D/A1
D/A2
D/A3
D/A4
D/A5
D/A6
D/A7
0
1
2
3
4
5
6
7
Any read to this register triggers an D/A conversion. This is a good method of starting
conversions from software or time of day clock control.
WRITE:
D/A Data can be written to this address and to Base + 1 to form a 12-bit
D/A data word. All eight DAC’s are updated using this register. The DAC
being updated is set via the Select bits (S3 to S0) in the Base +2 register.
READ:
Starts a D/A conversion. Updates the output of the selected DACs in Base
+ 2 Register.
BASE + 1 - DAC Value MSB (4 bits)
D/A8
D/A9
D/A10
D/A11
D/A12
X
X
X
0
1
2
3
4
5
6
7
WRITE:
Send DAC data.
READ:
Clear Interrupt Request bit at Base +4 bit D#3
BASE + 2 - DAC Select Register
S0
S1
S2
S3
CLR
X
X
X
0
1
2
3
4
5
6
7
WRITE:
Select the DAC to update
READ:
Read back Currently Selected DAC
S2: S0:
The data entered to registers base +0 and base +1 will be latched to the
DAC register defined by these bits (see table 5-1).
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