Z85233 Datasheet, PDF (278/317 Pages) Zilog, Inc. – The Zilog SCC Serial Communication Controller

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Application Note
Technical Considerations When Implementing LocalTalk Link Access Protocol
784
;subroutine to time out bit time 4.3 usec per bit
785
;register c contains the number of bits to be
786
counted down
;**********************************************
1
787 bittime:
788
push
af
;save status and a reg
789
push
bc
;save
790
push
hl
;save
791
;
792
ld
a,0d2h
;ctc1 int vector
793
out
(ctc1_cont),a
794
795
ld
a,11011111b ;
796
out
(ctc1_cont),a ;enable int
797
;select counter mode
798
;clk/trg edge starts with rising edg
799
;time constant follows
800
;software reset
801
ld
a,c
;reg c contains the number of bits
802
out
(ctc1_cont),a ;load the number of bits to be counted
803
;**
804
pop
hl
;restore
805
pop
bc
;restore
806
pop
af
;restate status and a reg
807
ei
808
ret
809
UM010901-0601
6-143