Measurement-computing CIO-DAS160x/1x Uživatelský manuál stáhnout pdf (Strana 26)

6.1.4 FOUR BIT DIGITAL I/O REGISTERS

BASE ADDRESS+3

A read and write register.

When read from...

DI0, TRIGDI1DI2, CTR0, GATEDI30011

01234567

READ

The signals present at the inputs are read as one byte, the most significant four bits of which are always

zero. The pins 25 (digital input 0) and 24 (digital input 2) digital inputs have two functions each.

The TRIG function of digital input 0 can be used to hold off the first sample of an A/D set by holding it

low (0V) until you are ready to take samples, which are then paced by the 8254. It can also be used as

the source of an external start conversion pulse, synchronizing A/D conversions to some external event.

When written to..

DO0DO1DO2DO3XXXX

01234567

WRITE

The upper four bits are ignored. The lower four bits are latched TTL outputs. Once written, the state of

the inputs cannot be read back because a read back would read the separate digital input lines (see

above).

NOTE

Since the digital inputs have multiple functions, use the digital input lines 0-3 with

care when you are also using the A/D converter.

The digital outputs are also used by the CIO-EXP32, 32-channel analog

multiplexer/amplifier.

6.1.5 D/A REGISTERS

D/A 0 REGISTERS

BASE ADDRESS +4

XXXXD/A0

LSB

D/A1D/A2D/A3

01234567

BASE ADDRESS + 5

D/A4D/A5D/A6D/A7D/A8D/A9D/A10D/A11

MSB

01234567

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 43 44

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Measurement-computing CIO-DAS160x/1x Uživatelský manuál Strana 26