SCD1284 datasheet(98/176 Pages) INTEL

98 / 176 page

CD1284 — IEEE 1284-Compatible Parallel Interface Controller

Datasheet

char

serv_type, vector, channel, status, char;

int

char_count, i;

vector = inportb(SVCACKR);

/* gen. ack and get vector (read LIVR) */

channel = inportb(RICR) >> 2;

/* extract channel number from the RICR*/

serv_type = vector & 0x07;

/* mask RIVR to get type (good/

exception)*/

switch (serv_type) {

case 3:

/* good data service */

char_count = inportb(RDCR); /* get number of characters in FIFO

for ( i = 1; i <= char_count; i++) {/* - read that number of

chars */

char = inportb(RDSR);

/* read char from FIFO */

/* Code here would put the character in a buffer of some sort for

each

* channel. That code would be dependent on system software design

* so it won’t be shown here; this code just shows how to

manipulate the

* CD1284 registers to implement the poll mode service

acknowledge. */

}

break;

case 7:

/* exception data service request */

status = inportb(RDSR);/* by definition, only one char; get

status */

break;

}

outportb(EOSRR, 0x00);

/* write dummy value to EOSRR to terminate

}

6.4.2

Serial Transmit Service

/* The transmit service acknowledge routine follows very nearly the same steps that

the receive service routine follows. The SVCACKT* input is activated to start the

service cycle, reading the contents of the TIVR, and the TICR is read to get the

channel number. */

service_txm( )

{

char

vector, channel;

int

char_count, i;

vector = inportb(SVCACKT);

/* retrieve and save transmit interrupt

value */

channel = inportb(TICR) >> 2;

/* extract channel number from the RICR*/

/* Buffer management code would set-up pointers to the next 12

* characters (maximum) to be sent on this channel. Again, buffer

* layout is system design dependent and won’t be shown here.

for ( i = 0; i < char_count; i++) {/* transmit FIFO can take 12 characters

outportb(TDR, *next_char++);

/* it is assumed that char_count and next_char is set up by buffer code

}

outportb(EOSRR, 0x00);

/* write dummy value to EOSRR to terminate

}

SCD1284 Datasheet(PDF) 98 Page - Intel Corporation

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