MIDI Port I/O Programming
5-7
Sending a Command
Commands are sent through the Command port to control the operation of the interface.
Before sending the command, the Status port must be polled.
Example code:
mov
dx,wMpuBaseAddx
;MPU-401 base I/O address
inc
dx
;Status port
Busy:
in
al,dx
;Read status port
test
al,40h
;Ready for output?
jnz
Busy
mov
al,bCommand
;Get command
out
dx,al
;Output command via Command port
As only the UART mode is supported, only two commands are recognized. These two
commands are Reset and Enter UART mode.