SN76489AN + Printer port =?

Master (196)

23-11-2018, 08:20

Hi, dear MSXers!
Is it possible to use the printer port to control SN76489AN ?
I was thinking of using SN76489AN which is a cheap complex sound generator chip, and the printer port with the jelly-bean text editor software with every MSX, it may be a much easier solution.
I would like to hear your opinion on this project

By lintweaker

Champion (362)

23-11-2018, 09:10

Hi,
I you need to read from the device, the parallel port on MSX has only one 1 bit for reading (busy signal). For writing you have the full 8 bits.

By ali6x944

Master (196)

23-11-2018, 09:21

oh
can I just right constantly to the chip without reading it?

By Grauw

Ascended (9677)

23-11-2018, 09:23

You can try to modify VGMPlay's Franky driver to send data to the printer port...

(You don't need read I/O.)

By gdx

Enlighted (4168)

23-11-2018, 09:30

It's easy and cheap to add a SN76489AN to the MSX using the following diagram.

There is no filter so there is a little noise but it's OK.
By cons SN76489AN needs to be initialized by software as below.

	ld	b,4
	ld	a,09Fh
Volume0:
	out	(03Fh),a	; Set the
	add	a,020h		; volume of SN76489AN
	djnz	Volume0		; to zero

So SN76489AN produces an unpleasant noise as long as this routine is not performed.
So you have to find a hardware trick to avoid that even if you use the printer port.

By ali6x944

Master (196)

23-11-2018, 10:07

why the use of the magnitude comparator?
and for the noise, a simple LC based filter and amplifier to compensate for the impedance of the LC filter.

By Grauw

Ascended (9677)

23-11-2018, 12:05

The above diagram is for connecting as a cartridge (not via parallel port), so the 74LS688 is there for the I/O port decoding (it maps it to 3FH). Same can be done with a few AND/OR gates.

By gdx

Enlighted (4168)

23-11-2018, 14:39

The printer port does not provide power and sound output becomes separate.
The simplest and cheapest way is to use the extension BUS but that is none on all MSX.

By zett

Hero (606)

23-11-2018, 15:10

use a simpl

done printer port for sound....