Zilog Z16C35 Bedienungsanleitung PDF herunterladen (Seite 290)

Application Note

Technical Considerations When Implementing LocalTalk Link Access Protocol

14-10

LISTING 2

600 ;*************************************************

601 ;Subroutine to transmit the llapenq packet

602 ;*************************************************

00000244 603 txenq:

604

00000244 f5 605 push af ;save status and a reg

00000245 c5 606 push bc ;save

00000246 e5 607 push hl ;save

608 ;

00000247 f3 609 di ;make sure that

610 ;no interrupt routine

611 ;nor should interrupt

612 ;occur during

613 ;this subroutine.

00000248 3e03 614 ld a,03h

0000024a d3e8 615 out (scc_cont),a ;WR3

0000024c 3ecc 616 ld a,0cch

0000024e d3e8 617 out (scc_cont),a ;8b/char,rx crc

618 ;enable,addrs src

619 ;and rx disabled

620

00000250 3e0a 621 ld a,0ah ;select WR10

00000252 d3e8 622 out (scc_cont),a

00000254 3ee0 623 ld a,11100000b ;idle with ﬂags

00000256 d3e8 624 out (scc_cont),a

625

626 ;****enable transmitter *****

00000258 3e05 627 ld a,05h ;select WR5

0000025a d3e8 628 out (scc_cont),a

0000025c 3e68 629 ld a,01101000b ;enable tx

0000025e d3e8 630 out (scc_cont),a

631 ;

632 ;

633 ;****enable rs-422 driver *****

00000260 3e05 634 ld a,05h ;select WR5

00000262 d3e8 635 out (scc_cont),a

00000264 3e6a 636 ld a,01101010b ;enable tx,

00000266 d3e8 637 out (scc_cont),a ;reset rts

00000268 00 638 nop

00000269 00 639 nop

640 ;nop’s needed to complete 4.3 usec

641 ;for 1 bit time enable of transmitter.

642 ;total delay=2*(7+11+4) T states at 10 MHZ

643 ;

644 ;****disable rs-422 driver for 2 bit times*****

0000026a 3e05 645 ld a,05h ;select WR5

0000026c d3e8 646 out (scc_cont),a

0000026e 3e68 647 ld a,01101000b ;enable tx, set rts

00000270 d3e8 648 out (scc_cont),a

649 ;

00000272 3e80 650 ld a,10000000b ;reset txcrc

00000274 d3e8 651 out (scc_cont),a

00000276 0601 652 ld b,01h ;delay count

00000278 653 csloop:

00000278 10fe 654 djnz csloop ;loop needed

655 ;to complete

656 ;8.6 usec min.

657 ;or 2 bit times.

658 ;****enable rs-422 driver for llap transmission*****

0000027a 3e05 659 ld a,05h ;select WR5

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UM011002-0808

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