National Instruments NI-488.2 Benutzerhandbuch

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 "ni488.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 

ibist

 function.