National Instruments NI-488.2 Benutzerhandbuch

© National Instruments Corporation

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

1.

Configure the device for parallel polling using the 

PPollConfig

 

call, 

unless the device can configure itself for parallel polling. The 
following example configures a device at address 3 to assert data line 5 
(DIO5) when its 

ist

 value is 1.

#include "decl-32.h"

char response;

Addr4882_t AddressList[2];

/* The following command clears the GPIB. */

SendIFC(0);

/* The value of sense is compared with the ist bit

of the device and determines whether the data 

line is asserted.*/

PPollConfig(0,3,5,1);

2.

Conduct the parallel poll using 

PPoll

,

 store the response, and check 

the response for a certain value. In the following example, because 
DIO5 is asserted by the device if 

ist

 is 1, the program checks bit 4 

(hex 10) in the response to determine the value of 

ist

.

PPoll(0, &response);

/* If response has bit 4 (hex 10) set, the ist bit

of the device at that time is equal to 1. If 

it does not appear, the ist bit is equal to 0. 

Check the bit in the following statement. */

if (response & 0x10) {

printf("The ist equals 1.\n");

}

else {

printf("The ist equals 0.\n");

}

3.

Unconfigure the device for parallel polling using 

PPollUnconfig

, as 

shown in the following example. In this example, the 

NOADDR

 constant 

must appear at the end of the array to signal the end of the address list. 
If 

NOADDR

 is the only value in the array, all devices receive the parallel 

poll disable message.

AddressList[0] = 3;

AddressList[1] = NOADDR;

PPollUnconfig(0, AddressList);