Measurement Computing CIO-DAS08-PGH - Manual (Page 18)

4.2 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 + 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 over-running the A/D
converter.
4.3 STATUS AND CONTROL REGISTER
BASE + 2 (Read / Write) Read Functions
MUX0 MUX1 MUX2 IRQ IP1 IP2 IP3 EOC
0 1 2 3 4 5 6 7
READ = STATUS
EOC = 1 the A/D is busy converting and data should not be read.
EOC = 0 the A/D is not busy and data can be read.
IP3 to IP1 are the digital input lines on the 37 pin analog connector.
IRQ is the status of an edge triggered latch connected to Interrupt Input (pin 24) of the analog connector. It is high (1) when a
positive edge has been detected. It can be reset to 0 by writing to the INTE mask at BASE + 2 write.
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