CD1283 Datasheet, PDF (50/94 Pages) Intel Corporation – IEEE 1284-Compatible Parallel Interface

CD1283 — IEEE 1284-Compatible Parallel Interface
When the SVCACK* is activated, the SVCREQP* is deactivated. If the SVCACKP* signal is not
activated, then the service request must be removed by clearing PpIreq (PIR[7]), and the source of
the interrupt must be determined by reading the LIVR, PIVR, or PIR. Regardless of the variation
performed, IntEn (PFCR[4]) must be toggled at the end of the service routine to inform the device
that the service routine has terminated.
service_par( )
{
char
livr_val;
if (inportb(SVRR & 0x08)) { /* check for active service request */
livr_val = inportb(LIVR) & 0x07;
switch (livr_val) {
case 4:
/* just the parallel channel
state-machine request is active */
service_par_chan();
break;
case 5:
/* just the data path pipeline
request is active */
service_pipeline();
break;
case 6:
/* both requests are active */
service_par_chan();
service_pipeline();
break;
default:
break;
}
outportb(PFCR, inportb(PFCR & 0xEF);/* terminate service ack. sequence
by */
outportb(PFCR, inportb(PFCR | 0x10);/* toggling IntEn bit in PFCR */
return(0);
}
}
50
Datasheet