SCI242.TXT

      PROGRAMMING ASSEMBLY CODES
               for the
     SEQUENTIAL 242 MIDI INTERFACE


1. To initialize the ACIA for MIDI:

  LDA #$03     ;Master reset
  STA $DE00
  LDA #$15     ;Setup for 1 start bit +
                 8 bits + 1 stop bit
  STA $DE00    ; and 31.25k Baud


2. To send MIDI OUT:

  LOOP
  LDA $DE02    ;Read ACIA status reg.
  AND #$02     ;Check transmit empty
                 flag
  BEQ LOOP     ;Loop until empty
  LDA MIDIBYTE ;Load in byte to send
  STA $DE01    ;Send MIDI OUT


3. To receive MIDI IN:

  LOOP
  LDA $DE02    ;Read ACIA status reg.
  LSR          ;Check receive full flag
  BCC LOOP     ;Loop until ready
  LDA $DE03    ;Read MIDI IN


4. To initialize the PIA:

  LDA MODE     ;Use control registers
                 to set up
  STA $DF01    ; operating mode.
  STA $DF03    ;Obtain mode from Table 1

5. To read drum clock input:

  LDA $DF01    ;Read control register
  BPL EXIT     ;Branch if no drum clock
               ;Falls thru if inter-
                 rupted by drum clock
  LDA $DF00    ;Clear interrupt flag bit

6. To read footswitch input:

  LDA $DF03    ;Read control register
  BPL EXIT     ;Branch if no 
                 footswitch press
  LDA $DF02    ;Clear interrupt flag