#define echo    $FFEF
#define kbd_data $D010
#define kbd_cr $D011
#define serial_ready $C000
#define serial_read  $C080
#define serial_write $C081

* = $C300
.dsb (*-end_of_apple1serial), 0

; teletype on apple-1
* = $C300
teletype_apple1 = $C300
  lda serial_read
wait
  lda serial_ready
  beq wait
  lda serial_read
  jsr echo
  jmp wait
end_of_teletype_apple1

; teletype on remote
* = $C400
.dsb (*-end_of_teletype_apple1), 0

* = $C400
teletype_remote = $C400
  lda #$FF
  sta serial_write
get_key
  lda kbd_cr
  bpl get_key
  lda kbd_data
  sec
  sbc #$A0
  sta serial_write
  jmp get_key
end_of_teletype_remote

; 0-255 repeating counter over TXD
* = $C500
.dsb (*-end_of_teletype_remote), 0

* = $C500
counter_remote = $C500
  ldy #$00
  sta serial_write
check_ready
  lda serial_ready
  beq check_ready
  tya
  sta serial_write
  iny
  jmp check_ready