58 lines
802 B
ArmAsm
58 lines
802 B
ArmAsm
|
|
//
|
|
// Tape (normal) helper routine - bit reading
|
|
//
|
|
// Returns bit in Zero flag, Carry set means error, on 0 bit .A is 0 too
|
|
//
|
|
|
|
|
|
#if CONFIG_TAPE_NORMAL
|
|
|
|
|
|
tape_normal_get_bit:
|
|
|
|
// Fetch the first pulse
|
|
|
|
jsr tape_normal_get_pulse
|
|
bcc tape_normal_get_bit_1
|
|
|
|
// First impulse was short, second should be medium
|
|
|
|
jsr tape_normal_get_pulse
|
|
bcs tape_normal_get_bit_error
|
|
|
|
// We have a bit '0'
|
|
|
|
// Carry flag already clear
|
|
lda #$00
|
|
|
|
// FALLTROUGH
|
|
|
|
tape_normal_get_bit_done:
|
|
|
|
sta VIC_EXTCOL
|
|
rts
|
|
|
|
|
|
tape_normal_get_bit_1:
|
|
|
|
// First impulse was medium, second should be short
|
|
|
|
jsr tape_normal_get_pulse
|
|
bcc tape_normal_get_bit_error
|
|
|
|
// We have a bit '1'
|
|
|
|
clc
|
|
lda #$06
|
|
bne tape_normal_get_bit_done // branch always
|
|
|
|
|
|
tape_normal_get_bit_error:
|
|
|
|
sec
|
|
rts
|
|
|
|
|
|
#endif // CONFIG_TAPE_NORMAL
|