SCD1284 datasheet(99/176 Pages) INTEL

99 / 176 page

IEEE 1284-Compatible Parallel Interface Controller — CD1284

Datasheet

6.4.3

Modem Service

/* The following routine services the modem change service request. Context switch

is set up by activating the SVCACKM* input, reading the MIVR. The routine reads the

MISR register to determine which modem signal(s) changed. Channel status is an

externally defined variable that this routine updates. */

service_mdm( )

{

char

vector, channel;

vector = inportb(SVCACKM);

/* retrieve and save transmit interrupt

value */

channel = inportb(MICR) >> 2;

/* extract channel number from the RICR*/

mdm_status[channel] = inportb(MISR);/* get status of which modem signals

changed */

outportb(EOSRR, 0x00);

/* write dummy value to EOSRR to terminate

}

6.5

Parallel Channel Service Routines

In most respects, the parallel channel functions in the same way as the two serial channels, but the

Poll mode operation is different. Its functions can be performed in a couple of ways. The MPU is

only involved with the parallel channel in performing interrupt generation services. All other

channel operations are completely separate. Since the MPU is involved in the interrupt structure,

aspects of its behavior must be taken into account.

SCD1284 Datasheet(PDF) 99 Page - Intel Corporation