Epple-II/share/Resources/rom/clock.m4

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YSAV1 = $35
CR = $8D
STKBAS = $0100
BUF = $0200
READC = $C080
LATCHC = $C081
CLOCK PHP
NOP
PLP
CLV
CLI
SEC
BVS *+2+$18
BVC READCL
NOP
WRITECL ORA ($6F,X)
RTS
READCL LDA #$60
STA YSAV1
JSR YSAV1
TSX
LDA STKBAS,X
ASL
ASL
ASL
ASL
TAX
LDY #0
LOOP LDA LATCHC,X
REREAD LDA READC,X
BPL REREAD
STA BUF,Y
INY
CMP #CR
BNE LOOP
RTS