Commodore 1570 User Manual page 105

; subroutines (refer to Cl28 User's Guide for SPINP and SPOUT vectors)
spout Ida mmureg
; change serial direction to output
ora #$08
sta mmureg
Ida #$7f
sta dlicr
; no irq's
Ida #$00
sta dltirnh
Ida #$03
sta dltirnl ; low 6 us bit (fastest)
Ida dIcra
and #$80 ; keep TOD
ora #$55
sta dIcra
; setup CRA for output
bit
dlicr ; elr pending
rts
spinp Ida dlcra
; input, 6526
and #$80
ora
#$08
sta
dicra
Ida
mmureg
and #$f7
sta
mmureg
; mmu serial direction in
rts
elklo Ida
d2pra ; set clock low
ora #clkout
sta d2pra
rts
clkhi Ida d2pra
; set clock high
and #$ff-clkout
sta
d2pra
rts
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