Epson PF10 problems
dave04a at dunfield.com
Fri Dec 23 10:24:18 CST 2005
> > I don't hve the PF10 so I can't offer specific help, however I will mention
> > that I have a few of the application ROMs for the PX-8 if you are
> > interested in the content.
> You got my attention with that one! Assuming that I can get this thing
> working again, that is...
I'll dig em out over the holiday and see if I can read them.
> > If you can get the exact CPU type, I may have a disassembler that will
> > let you peek into the startup code a little better.
> For which chips?
Lots! ("My day job is producing development tools for a large number of
> > Lastly, one little tool I have in my "homebuilt gadgets" box is a 28 pin
> > "plug" attached to a little board with a ROM socket ,a bit of logic and
> > a really dumb UART (the kind you setup in hardware).
> This sounds interesting. Which UART would that be? I'm vaguely remembering
> something of the sort, but can't remember the part number, and am pretty
> sure I don't have any, though I have lots of the other sort in various
I'd have to look at it to be certain (haven't had to write anything for it in a long time),
but I'm pretty certain I used a 6402 - but you could use any of the "hardare
programmable" uarts (AY-5-1013, COM2502 etc.) - You don't NEED to use a
"hardware programmable" uart, but doing so means that the only thing you need to
write is the data register. And with this setup, "writes" are best kept to a minimum :-)
> > What the logic does is map one 256 byte block to read the status (RX ready,
> > TX ready) and Data registers (you don't need 256 bytes for this but it
> > was easy), and one 256 byte block to write the data register (The
> > low byte of the address is the data you write). To make it work in
> > either "high vector" or "low vector" systems, it's worth putting on
> > jumper to move the block to either end.
> Hm. I'm not sure I grasp this completely, but it sounds interesting.
The idea is to have a "monitor" that you can plug into the EPROM socket
of just about any machine, and talk to it (assuming that you write code for
that particular CPU), and also to assume that the rest of the hardware is
unknown, and possibly not working.
It's possible to write a simple montor that does not use RAM, however you
still need a way to communicate with the debug terminal - since an EPROM
socket does not have a -WR line, you can't write in the "normal" sense -
also, you don't want to risk contention with something else on the bus.
So what I did was to generate selects for two 256 byte pages in the
ROM area - reading the top 1/2 of the first page gets me two bits
which are the RXready and TXready signals from the UART. Reading
the bottom 1/2 of that page gets me the receive data register. Reading
the second 256 byte page actually writes the bottom byte of the
address to the UART transmit data register - this allows me to read/write
to a terminal without having to do anything other than read the EPROM
space. This lets me get "inside the bus" and be able to do basic reads
and writes on most any system.
> > I've written a number of "Hardware Debug Monitors" which work on
> > this board, and don't use any RAM which enable me to to basic
> > Display/Write memory operations - With this tool, as long as the ROM
> > runs, you can "get inside" the BUS - Btw, I also include "loop read"
> > and "loop write" function - terminated by RESET - very handy when
> > debugging at this level.
> Since I have a whole pile of assorted 8-bit parts a ROM emulator was something
> I was thinking about. This stuff you describe sounds as if it might also be
> useful, too.
> Got more info up anyplace?
No more info about my "ROM socket monitor", as I built it a long time ago, and
don't even have schematics (at least I don't know where they would be) - but it
is pretty simple and should not take much to replicate.
As far as tools, assemblers, disassemblers, compilers, monitors etc. go - these are
described and have downloadable demos on my comercial site (www.dunfield.com)
- Yes, I generally expect people to pay if they want a complete package, however I
often give individual component tools to people who are doing a worthy cause (like
fixing a classic computer) and have a specific need.
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
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