23 Dec
2005
23 Dec
'05
8:39 p.m.
On Friday 23 December 2005 11:24 am, Dave Dunfield wrote:
I'll dig em out over the holiday and see if I can read them.
No rush, I still need to get that thing working...
Lots! ("My day job is producing development tools for a large number of
embedded processors).
Hmm.
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 :-)
Yeah, and it sure simplifies things when you don't need all that extra
"stuff" that the programmable ones give you. I should get a hold of a couple
of those chpis one of these days. Is that 6402 a single-supply part? I
guess I need to fetch a few more datasheets...
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 like it. :-)
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.
I think I've got a better idea of what you're talking about now...
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... 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? 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 families... 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. 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? 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.
I think I need to get some hardware together first, and maybe come up with
some kind of a simple eprom emulator...
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin