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Mon Jun 8 01:16:11 CEST 2009

Philips VG8020

This was my first computer.  I got a PC and got into C and x86 asm
before I ever got serious about Z80 assembler.  If I recall it was really
hard to get good information.  At one time there was a machine code
monitor listed in one of the magazines my uncle subscribed to, which
was my only source.  I keyed it in but couldn't get it to work.  A
major disappontment which scarred me forever ;)  I'd like to set that
straight and get Staapl running on the MSX.

To bootstrap it, the simplest way is probably the cassette interface:
it's FSK to a maximum of 2400 baud.  Should be quite easy to hook up
to a PC or a simple uC circuit.

The cassette tape input connects to the sound chip[3] through an
interface circuit consisting of a single opamp configured as a
schmitt-trigger.  The cassette input is bit7 in register14 of the PSG.
After bootstrapping with a standard "bload" format, this could be used
directly to read other digital formats.  Some more info here[4] and in
the MSX Red Book[5].

[1] http://www.funet.fi/pub/msx/docs/service_manuals/philipsvg802000sm.pdf
[2] http://msxbanzai.tni.nl/computers/philips.html
[3] http://en.wikipedia.org/wiki/YM2149
[4] http://msx.retro8bits.com/msxtape.html
[5] http://msx.retro8bits.com/msxarchives/aredbook.zip



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