Parallel polling with traditional ni-488.2 calls – National Instruments NI-488.2 User Manual

Page 93

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Chapter 8

NI-488.2 Programming Techniques

NI-488.2 User Manual

8-18

ni.com

Parallel Polling with Traditional NI-488.2 Calls

Complete the following steps to implement parallel polling using
traditional NI-488.2 calls. Each step contains example code.

1.

Configure the device for parallel polling using the

ibppc

function,

unless the device can configure itself for parallel polling.

ibppc

requires an 8-bit value to designate the data line number,

the

ist

sense, and whether the function configures the device for

the parallel poll. The bit pattern is as follows:

0 1 1 E S D2 D1 D0

E is 1 to disable parallel polling and 0 to enable parallel polling for that
particular device.

S is 1 if the device is to assert the assigned data line when

ist

is 1,

and 0 if the device is to assert the assigned data line when

ist

is 0.

D2 through D0 determine the number of the assigned data line. The
physical line number is the binary line number plus one. For example,
DIO3 has a binary bit pattern of 010.

The following example code configures a device for parallel polling
using traditional NI-488.2 calls. The device asserts DIO7 if its

ist

is 0.

In this example, the

ibdev

command opens a device that has a primary

address of 3, has no secondary address, has a timeout of 3 s, asserts
EOI with the last byte of a write operation, and has EOS characters
disabled.

#include "ni4882.h"

dev = ibdev(0,3,0,T3s,1,0);

The following call configures the device to respond to the poll on DIO7
and to assert the line in the case when its

ist

is 0. Pass the binary bit

pattern, 0110 0110 or hex 66, to

ibppc

.

ibppc(dev, 0x66);

If the GPIB interface configures itself for a parallel poll, you should
still use the

ibppc

function. Pass the interface index or an interface

unit descriptor value as the first argument in

ibppc

. Also, if the

individual status bit (

ist

) of the interface needs to be changed, use the

IbcIst

option with the

ibconfig

function.

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