RE: Looking for MSX2 expertise

["Andrew Lynch" <LYN...@YAHOO.COM>]

> -----Original Message-----
> From: cctalk-...@classiccmp.org [mailto:cctalk-
> bou...@classiccmp.org] On Behalf Of Alexandre Souza
> Sent: Monday, August 05, 2013 7:59 PM
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Looking for MSX2 expertise
> 
> > Honestly, I don't know much of anything about MSX.
> 
>     You should! This is a **very nice** computer for mostly anything.
> 
>     I'd reccomend you to take a look at something if you have time:
>     - BlueMSX emulator and its source code
>     - MSX Datapack (3 huge books in japanese, but some info and schematics
> well detailed in English)
>     - MSX Techinical Handbook (you can find an excellent scanned copy at
my
> site:
>     http://www.tabalabs.com.br/msx/msx_tech_hb/)
> 
> > Assuming we start with this as our baseline configuration 1.  N8VEM 8
> > slot active termination S-100 backplane 2.  S100computers.com and
> > N8VEM S-100 Z80 CPU board 3.  S100computers.com and N8VEM S-100 VDP
> > Are any changes necessary to the above boards to provide MSX and/or
> > MSX2 compatibility?
> 
>     I need to study the schematic of the boards. I'm travelling for work
right
> now. I'll download them and take a look.
> 
> > What else would be necessary to complete MSX and/or MSX2
> > compatibility?  I assume some sort of S-100 board with 64K SRAM + IO.
> > Probably a cartridge port, couple 8255 PPIs for control and ASCII
> > keyboard and a serial port for a mouse?  Is there any sort of
> > interrupt controller or DMA controller?
> 
>     The MSX is way simpler than that. Basically (for MSX1 compatibility)
you
> needs:
>     - A Z80 processor clocked at 3.579545MHz
>     - A AY-3-8910 chip (sound processor, but also used for cassete input
> [!])
>     - A 8255 PPI
>     - A TMS9128 (or compatible - you can use 9938 or 9958 processors since
> they are a superset of the 9128) video processor chip
>     - At least 16K of RAM (preferably 64K)
>     - A little of glue logic :o)
> 
>     Everything else is an expansion and MUST be glued to the expansion
bus.
> 
> > We can reuse the S-100 bus interface "glue" from other boards.  What I
> > am looking for is the components necessary for hardware compatibility.
> 
>     Maybe, but what is the objective of the project?
>     - Create a MSX?
>     - Create an add-on board for MSX compatibility to an S-100 computer?
>     - Creating something new? :D
> 
>     Greetings from Brazil :)

Hi Alexandre!  Thanks!  There are two objectives for the project

Primary objective: To supply the necessary hardware to complete MSX
compatibility at the hardware level on an S-100 bus system.  I believe this
would be a first.
Secondary objective:  a small general purpose SRAM and IO board to help with
debugging a simple system when paired with only a CPU board.

From what I read above it sounds like there needs to be a clock signal tie
in from the V9938 VDP to the Z80 CPU clock to supply the 3.579545 MHz
signal.  It is emitted from the V9938 if I recall correctly.  I am thinking
an "over the top" style wire jumper with the Z80 CPU board next to the VDP
on the S-100 bus.

Also the ongoing design of the S-100 VDP V3 may need to be modified for
cassette IO functions.  How are those implemented?   There are spare GPIO
pins on the AY-3-8910 so it makes sense if we are talking about motor
control, Push to Talk, etc.

A simple 64K SRAM + IO (8255 PPI + UART) would be perfect for not just MSX
compatibility but for builders in general as a CPU board debugging tool.

Thanks and have a nice day!

Andrew Lynch