Zilog Z16C35 - Manual (Page 288)

Application Note
Technical Considerations When Implementing LocalTalk Link Access Protocol
14-8
APPENDIX A
Listing 1- Asembler Code for SCC Initialization
LISTING 1
475 ;***************************************
476 ;subroutine to initialize scc registers
477 ;***************************************
000001e2 478 initscc:
000001e2 f3 479 di ;disable int while programming scc
000001e3 f5 480 push af
000001e4 c5 481 push bc
000001e5 e5 482 push hl
483
000001e6 3e09 484 ld a,09h ;WR9
000001e8 d3e8 485 out (scc_cont),a ;point to scc register
000001ea 3e80 486 ld a,80h ;channel reset
000001ec d3e8 487 out (scc_cont),a ;scc register value
000001ee 00 488 nop ;delay needed after scc reset
489
490
000001ef 21Wwww 491 ld hl,scctable ;fetch start of scc init table
000001f2 492 scc1:
000001f2 7e 493 ld a,(hl) ;fetch register pointer value
000001f3 feff 494 cp 0ffh
000001f5 caWwww 495 jp z,finscc ;if reg a =0ffh then initscc finished
000001f8 d3e8 496 out (scc_cont),a
000001fa 23 497 inc hl
000001fb 7e 498 ld a,(hl)
000001fc d3e8 499 out (scc_cont),a
000001fe 23 500 inc hl
000001ff c3R000+01f2, 501 jp scc1 ;loop back
502
00000202 503 scctable:
00000202 04 504 db 04h ;WR4
00000203 20 505 db 00100000b ;sdlc uses 1x,sdlc mode,no parity
506
00000204 01 507 db 01h ;WR1
00000205 00 508 db 00h ;nothing,rx,tx and ext int disabled
509
00000206 02 510 db 02h ;WR2
00000207 00 511 db 00h ;vector base is 00h
512
00000208 03 513 db 03h ;WR3
00000209 cc 514 db 0cch ;rx 8b/char,rx crc enabled,address
515 ;search mode for adlc address filtering
516 ;rx disabled.
517
0000020a 05 518 db 05h ;WR5
0000020b 60 519 db 60h ;tx 8b/char, set rts to disable drivers
520
0000020c 06 521 db 06h ;WR6
0000020d 00 522 db 00h ;address field=’myaddress’ in main pgm
523
0000020e 07 524 db 07h ;WR7
0000020f 7e 525 db 7eh ;flag pattern
526
00000210 09 527 db 09h ;WR9
00000211 01 528 db 01h ;stat low, vis therefore vector returned
529 ;is a variable depending on the source
530 ;of the interrupt.
531
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UM011002-0808