Measurement Computing Personal488 rev.3.0 For DOS & Windows 3.Xi - Manual (Page 196)

II. SOFTWARE GUIDES - 9. Driver488/SUB 9I. Operating Modes
Personal488 User’s Manual, Rev. 3.0 II-181
Status Indicator Description
“P” (Peripheral) Driver488 is in the Peripheral ( *CA ) operating mode.
“C” (Controller) Driver488 is the Active Controller ( CA ).
“T1” (Trigger) Driver488, as a Peripheral, has received a Trigger bus command.
“C1” (Clear) Driver488, as a Peripheral, has received a Clear bus command.
“T” (Talk) Driver488 is in the Talk state and can Output to the bus.
“L” (Listen) Driver488 is in the Listen state and can Enter from the bus.
“I” (Idle) Driver488 is in neither the Talk nor Listen state.
“G1” (Change) An Address Change has occurred, that is, a change between Peripheral
and Controller, or among Talk , Listen , and Idle has occurred.
This is, perhaps, the most useful interrupt in the Peripheral mode.
The following BASIC program fragment illustrates the use of the Address Change and Addressed State
indicators to communicate with the Active Controller.
First check Status until it indicates there has been an Address Change:
while (1) {
Status (ieee, &stat);
if (!stat.addrChange) { continue;}
if (stat.idle) {continue;)
/* If we are addressed to listen, we ENTER a line from the */
/* controller and print it out. */
if (stat.listener) {
Enter (ieee, data);
printf (“%d”, data);
printf (“\n”;
continue;
}
/* If we are addressed to talk, we INPUT a line from the keyboard*/
/* and OUTPUT it to the controller.*/
if (stat.talker) {
gets (message);
Output (ieee, message);
continue;
}
printf (Bad addressed state.\n”);
break;
}
It is also possible to detect these conditions with the Arm command and handle them in an Interrupt
Service Routine (ISR). The Peripheral , Controller , Talk , Listen , and Idle conditions cause
interrupts only when the Address Change indicator “G1” in the Status response is set. The Change ,
Trigger , and Clear indicators are all reset by the Status command. Thus, the Status command
should be used in the Interrupt Service Routine to prevent re-interruption by an indicator which has not
been reset.
The various Arm conditions and their descriptions are provided in the following table: