We are using the TNT5002 chip in our instrument device and implemented the ESP-488TL library code as supplied by NI. The device is setup for INTERRUPT mode. I have a code loop similar to NORMAL I/O and NORMAL ADDRESSING as in APPENDIX B of the ESP-488TL MANUAL. In normal message exchange between CONTROLLER APPLICATION (the PC) and my instrument device, the PC sends a DEL? query, the LACS bit turns on, the code RECEIVES the "DEL?" data query, processes it and then forms a message to be sent. When the TACS bit turns on, the message is sent using the SEND command. Everything works and we're synchronized.
1. When the PC sends a command only, the LACS bit turns on, and I receive the data then execute the command. HOWEVER, because I am in this message loop, the LISTENER is still addressed (the LACS bit stays turned ON), and so I continue to call the RECEIVE function but it returns a data count == 0. THe NRFD CONTROL SIGNAL on the bus also toggles every time the RECEIVE command is executed. Is this NORMAL BEHAVIOR? Should I be setting a control bit in the TNT5002 to stop this or should I be changing my program code to not keep sitting on the RECEIVE command? I am looking at this with the GPIB+ ANALYZER and have noticed that other instruments DO NOT toggle the NRFD control line when they are only sent a command unlike the behavior my instrument produces. Because I am in the loop, the timeout of 1 SEC occurs, a BUS ERROR BIT is generated, and continues endlessly because the RECEIVE command with datacount == 0 condition is true.
Thanks,
Victor
ATTACHED IS MY MESSAGE LOOP CODE:
while (1) { // MAIN() program while loop
////////////////////////////////////////////////////////////////////////////////
#ifdef ETHERNET_ENABLED
ENET_Handler()
// service the Ethernet
#endif
if ((ch = serEgetc()) != -1) // any chars available from MicroTerminal?
stateSER_CHAR = TRUE
// check Serial Port E
#ifdef GPIB_ENABLED
Update_INTERFACE_STATUS()
/* Update status word */
#endif
if (INTERFACE_STATUS&LACS) { /* If listener
addressed */
#ifdef DEBUG_MSGS
printf("gpib (listen) INTERFACE_STATUS =
0x%X\r\n",INTERFACE_STATUS)
#endif
Receive(buf,50,EOI)
/* Read up to 50 bytes */
// if TIMEOUT is disabled, then Receive may never return //
if (DATA_COUNT == 0) {
#ifdef DEBUG_MSGS
printf("DATACOUNT == 0\r\n")
#endif
} // endif DATA_COUNT == 0
if(DATA_COUNT>0) {
#ifdef DEBUG_MSGS
printf("\r\nReceived %lu data bytes\r\n",DATA_COUNT)
//sprintf(DISPLAY_LINE,"gpib (receive) %lu bytes \r\n",DATA_COUNT)
//prtTERM(DISPLAY_LINE)
#endif
for (i=0
i<DATA_COUNT
i++) {
gpibBUFFER_IN[i] = buf[i]
} // end for
gpibBUFFER_IN[i] = 0x00
// buf doesn't terminate so add NULL to mark end
stateGPIB_DATA_IN = TRUE
//indicate data from GPIB is here to process later
stateCMD_FROM_GPIB = TRUE
//command was from GPIB
} //end-if DATA_COUNT > 0
} // endif
else if(INTERFACE_STATUS&TACS) { /* see if TACS Talker
addressed */
/* Send data out only if it is available */
if (stateGPIB_DATA_OUT == TRUE) {
Send (gpibBUFFER_OUT,strlen(gpibBUFFER_OUT),EOI)
//send the data out
if(DATA_COUNT > 0) { /* If data bytes sent
print
it */
#ifdef DEBUG_MSGS
printf("\nSent %lu bytes\r\n",DATA_COUNT)
//sprintf(DISPLAY_LINE,"gpib (send) %lu bytes\r\n",DATA_COUNT)
//prtTERM(DISPLAY_LINE)
#endif
stateGPIB_DATA_OUT = FALSE
Clear_4882_Status(STB,0x10)
/* Clear MAV bit */
} //end-if
} //end-if
// what should be done if Talker Address and NO DATA available nor
will be available to be sent ??
} // endif
if (INTERFACE_STATUS & ERR) {
#ifdef DEBUG_MSGS
//sprintf(DISPLAY_LINE,"gpib (error) %d\r\n",INTERFACE_ERROR)
//prtTERM(DISPLAY_LINE)
printf("gpib (error) %d\r\n",INTERFACE_ERROR)
#endif
INTERFACE_STATUS &= ~ERR
INTERFACE_ERROR = INTERFACE_ERROR
} //end-if
//12.05.06
if (INTERFACE_STATUS & TIMO) {
#ifdef DEBUG_MSGS
printf("TIMO %d\r\n",INTERFACE_STATUS)
#endif
INTERFACE_STATUS &= ~TIMO
} //end-if
if (g_DEVICE_CLEAR) {
#ifdef DEBUG_MSGS
printf("g_DEVICE_CLEAR %d\r\n",INTERFACE_STATUS)
#endif
g_DEVICE_CLEAR = FALSE
DEVICE_CLEAR()
}
