Measurement-computing CIO-DAS16/330 Manual do Utilizador descarregar pdf (Página 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

TS0TS1DMADon’t CareIR1IR2IR4INTE

01234567

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)11

Start on rising TRIGGER (Digital input 0, Pin 25)01

Software triggered A/D only.X0

TS0TS1

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 33 34

Sem comentários

Measurement-computing CIO-DAS16/330 Manual do Utilizador Página 21