Sending Midi Data; Reading Midi Data - Creative SB0350 Programming Manual

5-10 MIDI Port I/O Programming

Sending MIDI Data

Once in UART mode, MIDI data can be sent to an external MIDI device by writing to
the Data port.
Example code:
Busy:

Reading MIDI Data

When MIDI data is available from an external MIDI device, it can be read in from the
Data port. There are two modes used in detecting the availability of input data: polling
and interrupt.
When in polling mode, as before, input data is available when bit 7 of the Status port is
zero. Conversely, when bit 7 is a one, no MIDI data is available.
In interrupt mode, an interrupt occurs when a MIDI code is ready. An interrupt service
routine has to be set up to retrieve the MIDI code. Reading from the Data port will
clear the interrupt signal.
The sequence for reading MIDI data is identical in both polling and interrupt modes.
Below is a code fragment that can be used in either the polling routine or the interrupt
service routine:
Busy:
Under the MPU-401 UART mode, there is no timing information available. It is up to
the application to handle the timing for the MIDI data.
mov dx,wMpuBaseAddx
inc dx
in al,dx
test al,40h
jnz Busy
mov al,bMidiData
dec dx
out dx,al
mov dx,wMpuBaseAddx
inc dx
in al,dx
test al,80h
jnz Busy
dec dx
in al,dx
;MPU-401 base I/O address
;Status port
;Read status port
;Ready for output?
;No
;Get MIDI data
;Data Port
;Output MIDI data
;MPU-401 base I/O address
;Status port
;Read status port
;MIDI data available?
;No
;Data port
;Read MIDI data, and clear interrupt