Specifications

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.