From abef6566e7feaac9287a75b2a3bc177dc7fa3c3f Mon Sep 17 00:00:00 2001 From: jede Date: Mon, 1 Mar 2021 22:45:05 +0100 Subject: [PATCH] Add revers.s --- libsrc/telestrat/revers.s | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 libsrc/telestrat/revers.s diff --git a/libsrc/telestrat/revers.s b/libsrc/telestrat/revers.s new file mode 100644 index 000000000..ad3e1f909 --- /dev/null +++ b/libsrc/telestrat/revers.s @@ -0,0 +1,37 @@ +; +; Ullrich von Bassewitz, 07.08.1998 +; +; unsigned char revers (unsigned char onoff); +; + + .export _revers + .export rvs + +; ------------------------------------------------------------------------ +; + +.code +.proc _revers + + ldx #$00 ; Assume revers off + tay ; Test onoff + beq L1 ; Jump if off + ldx #$80 ; Load on value + ldy #$00 ; Assume old value is zero +L1: lda rvs ; Load old value + stx rvs ; Set new value + beq L2 ; Jump if old value zero + iny ; Make old value = 1 +L2: ldx #$00 ; Load high byte of result + tya ; Load low byte, set CC + rts + +.endproc + +; ------------------------------------------------------------------------ +; + +.bss +rvs: .res 1 + +