Measurement Computing CIO-DAS08-AOH - Manual (Page 14)

Table 6-2. Register Functions
82C55 Control None BASE + 15
PORT C 82C55 PORT C 82C55 BASE + 14
PORT B 82C55 PORT B 82C55 BASE + 13
PORT A 82C55 PORT A 82C55 BASE + 12
DAC 1 High Byte (& individual update) Simultaneous Update BASE + 11
DAC 1 Low Byte Simultaneous Update BASE + 10
DAC 0 High Byte (& individual update) Simultaneous Update BASE + 9
DAC 0 Low Byte Simultaneous Update BASE + 8
Counter Control Not used BASE + 7
Load Counter 2 Read Counter 2 BASE + 6
Load Counter 1 Read Counter 1 BASE + 5
Load Counter 0 Read Counter 0 BASE + 4
Programmable gain control Channel MUX and Gain Status BASE + 3
OP1 - OP4, INTE & MUX Address EOC, IP1 - IP3, IRQ, MUX Address BASE + 2
Start 12 bit A/D conversion A/D Bits 1 (MSB) - 8 BASE + 1
Start 8 bit A/D conversion A/D Bits 9 - 12 (LSB) BASE
WRITE FUNCTION READ FUNCTION ADDRESS
6.2 A/D DATA REGISTER
BASE ADDRESS (Read / Write)
0 0 0 0 A/D12
LSB
A/D11 A/D10 A/D9
0 1 2 3 4 5 6 7
READ
On read, it contains the least significant four digits of the analog input data.
These four bits of analog input data must be combined with the eight bits of analog input data in BASE + 1, forming a
complete 12 bit number. The data is in the format 0 = minus full scale. 4095 = +FS.
WRITE
Writing any data to the register causes an immediate 8-bit A/D conversion.
BASE ADDRESS + 1 (Read / Write)
A/D8 A/D7 A/D6 A/D5 A/D4 A/D3 A/D2 A/D1
MSB
0 1 2 3 4 5 6 7
READ
On read the most significant A/D byte is read.
The A/D Bits code corresponds to the voltage on the input according to the table below.
0 Volts - Full Scale 0 0
½ Full Scale 0 Volts 800 2048
+ Full Scale + Full Scale FFF 4095
UNIPOLAR BIPOLAR HEX DECIMAL
WRITE
Writing to this register starts a 12-bit A/D conversion.
A note of caution: Place several NO-OP instructions between consecutive 12-bit A/D conversions to avoid overrunning the
A/D converter.
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