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From: Rich Webb on 19 Oct 2009 13:55
On Mon, 19 Oct 2009 17:01:50 GMT, nico(a)puntnl.niks (Nico Coesel) wrote:

>"Commander Dave" <cmdr-dave(a)spamcop.net> wrote:
>
>>"Nico Coesel" <nico(a)puntnl.niks> wrote in message
>>news:4adb732b.902338000(a)news.planet.nl...
>>
>>> Wiring a PLCC socket is not more difficult than a DIP socket.
>>
>>Oh, I don't know about that... it was definitely harder for me, but again,
>>I'm a newbie at building boards. Another reason I wanted the DIP 40 format
>>was so I could breadboard it initially... those PLCC sockets don't fit on a
>>breadboard AFAIK. Since I have an adapter on the way (found one for $6.95
>>shipped), it's pretty much a moot point now.
>
>Indeed. But through hole PLCC sockets also use a 0.1" grid so they
>should fit on you breadboard.
>
>>>You'll need to figure out which pin goes where first though. I suggest you
>>> get a simple oscilloscope (a 20MHz will do) to do some measurements
>>> (like the port decoding).
>>
>>I would like to get an oscilloscope, but I am really cash poor. I
>>practically have to scrounge money for the small parts that I buy. One of
>>these days I'll snatch one up cheap, but until I get the money I have to
>>work with what I have.
>
>Or you could buy or a built a logic probe so you can at least see the
>level of a signal and whether it is changing.

Indeed, one can do a lot with just a logic probe. With one, it becomes
possible to have some answers to basic questions like: Is the chip
getting a clock at all? Or, is there an occasional write strobe?

Radio Shack used to carry them (hands up, everybody who is surprised
that they don't any more) but there are some inexpensive on-line sources
such as <http://www.web-tronics.com/logicprobes.html>
and <http://www.tequipment.net/TMTLogicProbes.html>

--
Rich Webb Norfolk, VA
From: Commander Dave on 19 Oct 2009 19:15

"petrus bitbyter" <pieterkraltlaatditweg(a)enditookhccnet.nl> wrote:

> The original Z80 UART (USART) is the Z80SIO. A powerful device yet hard to
> program correctly and it requires an external Baud-rate generator.

When I was considering UART's and based on my low level of experience, I
decided against the Z80SIO because it looked to be much more complex than
other solutions.

> Instead of that Z80SIO an Intel 8251 was often used. Much easier to
> program
> though it has some bugs like all Intel UARTS and their clones at the time.
> It also requires a Baudrate generator.

I considered the 8251 as there are tons of old Z80 books with instructions
on exactly how to interface and program the 8251 to the Z80. I decided
against it because the 8251 seemed to be an old chip and I wanted to try to
stay with something that would be easily obtainable from mainstream
companies like Digikey.

> FAIK the 16550A was the first bugfree type. I
> guess your 16C550 to be a clone of that last one. As they were used in PCs
> there's a lot of information about them on the net. Look for instance at:
> http://www.beyondlogic.org/serial/serial.htm

I think I have this site bookmarked already, but thanks for the link. Lots
of helpful information there. :-)

> If I had to deal with those old hardware I'd go for a 8251 using a 4060
> for
> the Baudrate generator as IMHO it is the most simple approach. As you have
> that 16C550 already I guess you will stick at it.

Yeah, got to stick with it in this incarnation at least. As I said a few
lines up, I didn't go for the 8251 because I am thinking it is an obsolete
part and it might not be readily available from mainstream sources. I wanted
to stick with parts I could get from a mainstream company. I mainly was
wondering if there was anything better and newer than the 16C550 that I
should have used.

> Which brings me to the main question: What do you really want to do?
> Because
> adding a serial interface to the existing hardware does not solve anything
> on its own. You will need to program a kind of monitor in the Gorf that
> communicates via that interface. Accepting commands and returning results.
> Then, when you want the Gorf to perform its original function, you need to
> get the firmware via the serial interface, store it in RAM and then pass
> control to it. I do not know the hardware of that Gorf but I suppose you
> will need to do some real hardware modifications. Not to mention the
> requirements if you want to do some debugging.

A fellow named Don posted the same question yesterday. I like to modify the
code on the Gorf machine and it has been a hassle in the past to burn a new
EPROM every time I wanted to test on real hardware. I want to have a serial
port attached so I can download code into memory.... kind of a dump and
execute type thing. I have modified the original game code so it looks for
an extra EPROM in a vacant socket if the debug switch is on. If it is there,
it jumps to my code, if not, it just resumes the normal game diagnostics. I
would have a monitor/debug program in the extra EPROM to control the serial
port. In case you are curious, I have ruled out a Z80 ICE and a EPROM
emulator for various reasons, not because they aren't a good idea, but for
other personal reasons (which I think I covered in previous postings if you
are curious).

> I do not know the hardware of that Gorf but I suppose you
> will need to do some real hardware modifications. Not to mention the
> requirements if you want to do some debugging.

Actually, since the Gorf machine already has static RAM (and some dynamic
also) on board, the only hardware mods is the connections to the bus from
the bottom of the cardcage (about 20 signal wires), power connections (again
from the card cage power connector) and the custom EPROM's which are all in
original sockets. One of my goals was to make as few changes to the original
hardware as possible. As for the debugging, most would be done with the MAME
emulator and only code that worked on the emulator would be tested on real
hardware which usually requires minimal debugging (just a tweak or two). A
simple monitor/debug program would be enough to do the job for me.

> BTW. Next time you want to post the same question in several newsgroups,
> address them all at once instead of one at a time.

Yeah, that's my bad. When I first started looking for an electronics
newsgroup to post in, I went to rec.electronics. Then I saw that it was
pretty dead there, but then found another I thought might be better and
posted it there. Then I found another and another and posted in those. I was
a real cluster-flub on my part, but next time I will know which groups are
active and will post to all at once as you have suggested. I apologize for
the inconvenience.

> petrus bitbyter

Thank you for your help and suggestions!
-Commander Dave


From: Nico Coesel on 20 Oct 2009 13:37
"Commander Dave" <cmdr-dave(a)spamcop.net> wrote:

>
>"petrus bitbyter" <pieterkraltlaatditweg(a)enditookhccnet.nl> wrote:
>
>> The original Z80 UART (USART) is the Z80SIO. A powerful device yet hard to
>> program correctly and it requires an external Baud-rate generator.
>> get the firmware via the serial interface, store it in RAM and then pass
>> control to it. I do not know the hardware of that Gorf but I suppose you
>> will need to do some real hardware modifications. Not to mention the
>> requirements if you want to do some debugging.
>
>A fellow named Don posted the same question yesterday. I like to modify the
>code on the Gorf machine and it has been a hassle in the past to burn a new
>EPROM every time I wanted to test on real hardware. I want to have a serial
>port attached so I can download code into memory.... kind of a dump and

Did you ever consider an eprom emulator?

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn't fit, use a bigger hammer!"
--------------------------------------------------------------
From: Commander Dave on 20 Oct 2009 19:12

"Nico Coesel" <nico(a)puntnl.niks> wrote in message
news:4addf484.1066523359(a)news.planet.nl...
>
> Did you ever consider an eprom emulator?

Yes, and decided against it for various personal reasons. I covered that
ground in previous posts if you are curious.

Thanks,
-Commander Dave


From: CellShocked on 20 Oct 2009 20:44
On Tue, 20 Oct 2009 17:37:05 GMT, nico(a)puntnl.niks (Nico Coesel) wrote:

>"Commander Dave" <cmdr-dave(a)spamcop.net> wrote:
>
>>
>>"petrus bitbyter" <pieterkraltlaatditweg(a)enditookhccnet.nl> wrote:
>>
>>> The original Z80 UART (USART) is the Z80SIO. A powerful device yet hard to
>>> program correctly and it requires an external Baud-rate generator.
>>> get the firmware via the serial interface, store it in RAM and then pass
>>> control to it. I do not know the hardware of that Gorf but I suppose you
>>> will need to do some real hardware modifications. Not to mention the
>>> requirements if you want to do some debugging.
>>
>>A fellow named Don posted the same question yesterday. I like to modify the
>>code on the Gorf machine and it has been a hassle in the past to burn a new
>>EPROM every time I wanted to test on real hardware. I want to have a serial
>>port attached so I can download code into memory.... kind of a dump and
>
>Did you ever consider an eprom emulator?

Mame, the arcade machine emulator, emulates several processors, and the
"rom" files are all just files. No more chips.

We are even emulating the Laser Disc based games now.

It is also a great exercise for your programmers to examine the source
code of. With all the CPUs emulated, it is interesting to examine each
processor's code module.
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