SFG05 Access

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Van erwinmusik

Master (140)

afbeelding van erwinmusik

04-07-2014, 21:05

Quote:

had a late night disassembling the SFG-05 BIOS, and wrote the following article on the MSX Assembly Page with my findings:
Yamaha YM2148, SFG-05 MIDI interface

cool Cool

Van Grauw

Ascended (10581)

afbeelding van Grauw

04-07-2014, 22:13

erwinmusik wrote:

SFG-01......MIDI is full functional, as Abduls DMS1 shows formidable.

erwinmusik wrote:

But as Abdul wrote, he does his program almost complete with DI.
Wether he uses his own timer or the timer of the modul. But without interupt handling for MIDI

Yeah but this kind of interrupt-less mode of operation is very hard to work with except in very cleverly and carefully coded special-purpose software like DMS1.

erwinmusik wrote:

And the MBIOS 1.1 initialisation of the SFG05 says, IM1 compatibility to SFG01.

Yup, but if I understand correctly, in the MBIOS 1.x IM1 modes it does not actually use interrupts or circular data buffers for MIDI. So to receive data, you have to manually poll for it in time to receive it (at 3125 bytes / seconds). That’s not practical.

In the SFG-05 the BIOS offers this 2.0 IM2 mode of operation, which does nicely read and write data on interrupts to and from circular buffers. I just wonder if technically, in hardware, this is already possible on the SFG-01, if you just directly access the hardware rather than depending on the BIOS. Or whether it is technically impossible, e.g. because they forgot to wire up the IRQ signal.

I’m asking because I wonder when I implement SFG-05 MIDI support in Synthesix, if it will work on the SFG-01 as well. Well, maybe the easiest thing is just to make it and then ask an SFG-01 owner to test it for me Smile.

Van erwinmusik

Master (140)

afbeelding van erwinmusik

04-07-2014, 22:06

I found this on grauw´s site:
interrupts
Very helpful for me and answers a lot of questions for me....

Van Grauw

Ascended (10581)

afbeelding van Grauw

04-07-2014, 22:11

Nice Cool. It’s originally a Dutch article by Ramon v/d Winkel that I translated to English two months ago. Glad you were able to find it!

Van erwinmusik

Master (140)

afbeelding van erwinmusik

04-07-2014, 22:17

I love those "simplified" Websites and go through. No Java, no Flash, nothing. That is absolut practicable to work with.
rarely to find today....

Van Latok

msx guru (3867)

afbeelding van Latok

05-07-2014, 00:48

erwinmusik wrote:

I love those "simplified" Websites and go through. No Java, no Flash, nothing. That is absolut practicable to work with.
rarely to find today....

Can't agree more!! Well said!

Van Grauw

Ascended (10581)

afbeelding van Grauw

06-07-2014, 02:06

Grauw wrote:

p.s. I wonder about the SFG-01. I have read that its MIDI support is limited because it does not support MIDI interrupts. Yet it also uses the YM2148, as per this photo. So, is the problem that the IRQ signal isn’t hooked up? Or is the hardware actually fully functional, and is it simply a BIOS software problem? Anyone knows? I don’t have one to test with myself unfortunately.

Looking at the SFG-01 schematics in the CX5M service manual, the /IRQ signal is hooked up between the cartridge connector and the YM2148. Also, comparing a photo of the board with photos of the SFG-05, it looks identical (except one has an extra board bolted-on the SFG-05 with two extra EPROMs — I guess an earlier revision). In the schematics, the only difference is an extra address line (A14) to the ROM and an extra condensor near the YM2148 clock input.

So, it looks good! I think MIDI interrupts on the SFG-01 will work!

Van maxis

Champion (512)

afbeelding van maxis

06-07-2014, 10:37

Grauw wrote:

I think MIDI interrupts on the SFG-01 will work!

In IM2 too Smile

Van Grauw

Ascended (10581)

afbeelding van Grauw

06-07-2014, 20:38

I updated the Yamaha YM2148 article:

1. Describe function of command registers 0 and 2: they enable / disable Tx and Rx.
2. Confirmed that the buffer size is just a single byte (like most other serial interfaces on MSX).
3. Remark that error flags do not influence interrupts.
4. Include the SFG-01, as it does not seem to have any limitations hardware-wise.

What’s left is to figure out what command bits 5 and 6 do, and it needs to be confirmed that framing errors do not place an invalid byte in the buffer.

Van Daniel Lionius

Supporter (6)

afbeelding van Daniel Lionius

14-05-2017, 23:00

Great topic.

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