Real Time Devices AD1200 User Manual page 40

Defining the VO Map
The I/O map for the ADl200 and ADA1200 is shown in Table 4-1 below. As shown, the board occupies 16
consecutive I/O port locations. The base address (designated as BA) can be selected using DIP switch S I as de-
scribed in Chapter l, Board Settings. This switch can be accessed without removing the board from the computer.
S 1 is factory set at 300 hex (768 decimal). The following sections describe the register contenrs of each address used
in the I/O map.
."Table /t-1 --ADl200/ADA1200 t/O Map
Reglster Description
Read Function
Write Function
Address'
(Declmal)
Read Status/Start Convert Read slatus word
Start A/D conversion
B A + 0
Read Data/Update DACs
Read converted data, LSB
first, then MSB
Simultaneously update
DAC 1 and DAC2
(ADA1200 only)
B A + 1
Reset
Not used
Resets board so that it is
ready to start A/D conversions B A + 2
Reserved
Not used
Not used
B A + 3
8255 PPI Port A
Read Port A dighal input lines
Program Port A digitaloutput
lines
B A + 4
8255 PPI Port B
(Ghannel/Board
Functions) R ead Port B bits
Program channel; external
trigger enable, IRQ enable
B A + 5
8255 PPI Port C
Read Port C digital input lines
Program Port C digital output
lines
B A + 6
8255 PPlControlWord Not used
Program PPI configuration
B A + 7
S2S4TimerlCounter 0
(Used for pacer clock)
Read count value
Load count register
B A + 8
8254Timer/Counter
1
(Used for pacer clock)
Read count value
Load count register
B A + 9
8254 Timer/Counter 2
(Available for external use) Read count value
Load count register
B A + 1 0
S254TimerlCounter
ControlWord
Not used
Program counter mode
BA + 1'l
D/A Converter 1 LSB
(ADA1200 only)
Not used
Program DAC1 LSB
B A + 1 2
D/A Converter 1 MSB
(ADA1200 only)
Nol used
Program DAC1 MSB
B A + 1 3
D/A Converter 2 LSB
(ADA1200 only)
Not used
Program DAC2 LSB
B A + 1 4
D/A Converter 2 MSB
(ADA1200 only)
Not used
Program DAC2 MSB
B A + 1 5
* BA = Base Address
4-3