Measurement Computing CIO-DAS16/330 - Manual (Page 21)

4.14 DIGITAL INPUT & OUTPUT
There are four bits of output only and four bits of input only on the CIO-DAS16/330 analog connector. From the original
DAS-16 design, these were the only eight bits of digital I/O.
For complete programming information refer to the section on CIO-DAS16/330 registers.
4.14.1 OUTPUT
The output bits are part of chip U39, a 74LS197 output buffer. The other half of the chip is used for on-board control. If
the digital output lines are blown by overload or high voltage connection, you can replace the chip.
4.14.2 INPUT
The input bits are part of chip U38, a 74LS244 buffer. The other half of this chip is used for on-board functions. This
chip is socketed.
4.15 INTERRUPT & TRIGGER CONTROL
The interrupt and trigger control is accessible via programming at register BASE + 9. Interrupts are enabled by setting
bit 7. The PC bus interrupt number, 2 to 7, 10, and 11, is register-programmed. The source, either from the 8254 or
external, is programmed also.
BASE ADDRESS +9
TS0 TS1 DMA Don’t Care IR1 IR2 IR4 INTE
0 1 2 3 4 5 6 7
A read and write register.
READ
INTE = 1, Interrupts are enabled. An interrupt generated will be placed on the PC bus interrupt level selected by IR4,
IR2, and IR1. When INTE = 0, interrupts are disabled.
IR4, IR2, IR1 are bits in a binary number between 0 and 7 which map interrupts onto the PC bus interrupt levels 2 - 7.
Interrupts 0 maps into 10 and interrupt 1 maps into 11.
TS1 & TS0 control the source of the A/D start conversion trigger according to Table 4-4 below.
Table 4- 4. A/D Start Conversion Source Coding
Start on Pacer Clock Pulse (CTR 2 OUT, no external access) 1 1
Start on rising TRIGGER (Digital input 0, Pin 25) 0 1
Software triggered A/D only. X 0
TS0 TS1
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