National Instruments NI-488.2 - page 111

GPIB Programming Techniques Chapter 7
NI-488.2 User Manual for Windows 7-12 © National Instruments Corp.
Parallel Polling with NI-488.2 Routines
Follow these steps to implement parallel polling using NI-488.2 routines. Each step
contains example code.
1. Configure the device for parallel polling using the PPollConfig routine, 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.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 = 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 the PPollUnconfig routine 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);