I made a mistake..! Wrongly inserted HCT32 on the Pageable ROM board.

[Chris Groenewegen]

Hello all, 

For whatever silly reason and after many checks I missed the fact that I wrongly inserted U4 (HCT32) on the Pageable ROM board. So ... upon feeding the board 5V and the PI Zero booted up with: all fine, keyboard found but waiting for UART. I did smell something vagely after 5-10 seconds and unplugged and immediately found the TOO hot U4. Replaced it with a new one but.... nope. Replaced the Z80 but nope still nothing. The Pi Zero seems fine as it does boot up and indicates to be waiting for the keyboard. Went back to original boards (not the CP/M upgrade kit) but also to no avail. I did need to flip back one of the Alliance Memory chips as I did not have spares on those. Clock seems fine at 7.38Mhz but A15 keeps running at 232Khz so I guess somewhere it's looping???? What other tests can I do?

[J.B. Langston]

If you have a TL866 ROM programmer, you can try reading out the contents of the ROM and verifying it against an image from the RC2014 github repo.  The TL866 can also be used to verify the functionality of RAMs and logic chips, so you could find any other bad chips that way. If you don't have one, they're very handy and can be found for as low as $50-60 on Amazon and probably cheaper on eBay.

Without that or something similar it may be difficult to figure out where the problem is.  You say you wrongly inserted it, by which I assume you mean it was in the wrong orientation? If so, you might look at the pinout of the chip and the schematic for the ROM board, and note any chips where having the chip in the wrong orientation would connect two outputs together, which could have potentially damaged those outputs.

[Mark T]

I think a reversed chip would hold all pins at 0.6v due to diodes to substrate on inputs and outputs. So in addition to shorting the outputs of u1 and u5 this could also permanently enable the eprom data outputs to the bus and possibly cause bus contention.

It might be safer not to swap components on the bus one at a time, as one damaged component could cause damage to the new part you swap in.

Maybe try removing all components from the bus except z80, use pull down, up resistors on data, and see if the z80 can run NOP and RST 38, if you can check on address lines with scope or possibly logic probe.

Verify rom and ram as JB suggested using programmer.

I think that would leave the uart as suspect. Not sure how you could verify that.

Mark

[Chris Groenewegen]

Thank you all for your comments and suggestions:

1. I bricked my TL866 just a day before this happened through the known process of upgrading to V6.85 and not yet been able to restore to a workable solution

2. Going back to my original RC2014 with the spare components I did manage to get it working. The RAM chips seem all fine and the original ROM also and I get it working through the FTDI UART and all is fine. 

3. Connecting it then with the Pi ZERO to a screen and keyboard is no luck..... :-(  keyboard is recognized etc. When pressing the reset button on the RC2014 nothing happens. Can I have botched up the PiZero Terminal Module? I would imagine not as it boots-up normally and the keyboard is recognized and then waiting for UART Data ... 

Should I be able to test the CP/M with the 64K ram and the normal UART board? If so that doesn't work so I suspect that the ROM is botched up now or perhaps even more 74HCT32 on the pageable ROM board?

[karlab]

If you have bricked your TL866, there is a way to restore it.

You have to open it and make a patch. Its decribed on the webpage.

http://www.autoelectric.cn/en/note.html

Karl

[Chris Groenewegen]

I tried that twice but to no avail. I keep getting the message to go to the Menu -> Tools -> Flash the firmware. I've been at the EEVBLOG already to read and re-read the tips and suggestions. Thanks though for feeding me tips. Appreciate it.

[karlab]

Sounds like the PiZero Term module is the problem.

Could be a bad connection somewhere.

The module carries only a few signal lines so it should relatively easy and check the connections.

Karl

[Chris Groenewegen]

Hi Karl, that also might be the issue however I do not get the normal full monty set-up working over the FTDI as well yet so still ploughing through. The pageable ROM board now seems to work with the 64KRAM also in. It does now recognize the original RC2014 ROM as well as the version with the HexLoader I created a while ago. Little by little I'm resolving the problems. I did exchange some more logic IC's on the ROM board. Tested both RAM chips on the normal smaller 32KRAM board from the original kit. 

Too bad my TL866 is botched so I can not check nor re-program a new ROM for CP/M.

[Karl A. Brokstad]

Is YouTube 866 broken or just Bricked? Did you check the link in my other post?

You only need one ROM image, and that is Steve Cousins SCMonitor.

Karl

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[Karl A. Brokstad]

YouTube read your

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[Chris Groenewegen]

Hi Karl, et al,

after a 5th attempt, not sure why now, I managed to get the TL866 working again. The ROM's all seem to be fine. I also tested the logic IC's on the Pageable Board and RAM board and they are fine (except for one) according the test button on the TL866. I tested the 2 RAM chips and this is also fine. However the whole set-up does not work yet. I now start to suspect for instance the ZIF socket as the old ROM's once did work well in this board but not anymore. Using the original ROM board with the new R0001009 ROM (CP/M full monty upgrade kit) does work perfectly in the ROM board when selecting the SCMonitor. One question I do have is if the Logic IC's versions are highly critical in terms of brand/speed. I believe I did match them back correctly with HCT versions but the brand not and certainly the origin (China eBay) is perhaps not reliable. Other observation I have is that  Z8400 Zilog IC did not work as well (yet).

So getting there slowly. Your suggestions and tips are still welcome!! :-)

On Monday, March 4, 2019 at 4:07:23 PM UTC+1, karlab wrote:

Is YouTube 866 broken or just Bricked? Did you check the link in my other post?

You only need one ROM image, and that is Steve Cousins SCMonitor.

Karl

Sent from my iPad

On 4 Mar 2019, at 15:22, Chris Groenewegen <cbj.gro...@gmail.com> wrote:

Hi Karl, that also might be the issue however I do not get the normal full monty set-up working over the FTDI as well yet so still ploughing through. The pageable ROM board now seems to work with the 64KRAM also in. It does now recognize the original RC2014 ROM as well as the version with the HexLoader I created a while ago. Little by little I'm resolving the problems. I did exchange some more logic IC's on the ROM board. Tested both RAM chips on the normal smaller 32KRAM board from the original kit. 

Too bad my TL866 is botched so I can not check nor re-program a new ROM for CP/M.

On Monday, March 4, 2019 at 3:04:37 PM UTC+1, karlab wrote:

Sounds like the PiZero Term module is the problem.

Could be a bad connection somewhere.

The module carries only a few signal lines so it should relatively easy and check the connections.

Karl

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[karlab]

Hi Chris

Since you got your T866 working again, do yourself a favor and burn SC Monitor R1.

Just to help you get the kit running.

So you found one IC not working, that may be the problem.

In general if you have a HCT version of a logic gate, it should work regardless of brand

I several brans in my setups and it doesnt make any difference.

The problem with China/ebay, is that the chip can be relabelled from LS to HCT to meet the market supply.

If this is the case you have been unlucky, I have bought ICs from China/eBay but not experienced this.

Karl

[Bill Shen]

Static discharge is a problem especially in the winter with the warm, dry indoor air.  It is an insidious problem because most of times it does not kill the device outright, but causing greater leakage currents, lower input impedance and weaken output drive.  CMOS is more sensitive to static than TTL.  Static damaged devices may still pass OK on a simple tester like TL866.  One method of flushing out static damaged parts is to run continuous diagnostic at high voltage (5.5V), hot (50 degree C) and for days (this is assuming the original working units are able to run at high voltage and high temperature).  If it survives the treatment, chances are it will do well in nominal conditions for years to come.
  Bill

[Chris Groenewegen]

Hi Karl,

Your figure #1 is perfectly do-able. Your figure #2 not. I've seen those in the Small Computer Monitor manual but 2nd figure does not work for me. I'm missing the jumper/link yes or no indication on the RAMboard at the bottom btw. What also DOES work is the pageable ROM board with the normal original RAMboard in. I will re-test the workings with the different RAM ICs now but am puzzling to identify the root cause here.

Chris

[Chris Groenewegen]

Hi Karl, further update... I used the 64K RAMboard in the 32KRAM configuration as stated here: https://rc2014.co.uk/modules/64k-ram/

That works perfectly too ' If only 32k is required, only IC1 (74LS32), IC2 (62256) and IC4 (74LS04) need to be fitted and all the jumper pins can be ignored." 

So something is odd here and either one of the logic ICs is bad U5 or IC5 or the backplane is wrong or still some logic on U1 or .... well not sure anymore.

[Karl Albert Brokstad]

Hi Chris

The pictures was taken from Steve’s documentation, and I just selected two of the many possible configurations.

I wasn’t sure what modules you had, try other configurations and other ROMs.

From SCMon you can page in and out memory, dump memory, start RAM test, start BASIC or CP/M and so on.

Karl

[Chris Groenewegen]

I'll try that another time. I just finished re-testing the Full CP/M kit and it was behaving intermittently. Only the message appears, via the serial terminal no the PI-Zero and then the whole thing hangs again. There must be something awkward still with the timings or perhaps a botched up ROM IC (from the KIT) although when reading it with the TL866 it seems fine. Perhaps the paging is still an issue and that could probably be related to the logic IC's on both the ROM and RAM board?

I can run it now per your configuration #2 here as per your suggestion. Plodding through still. Will keep you all posted. Regards, Chris

[Karl Albert Brokstad]

If the serial send out the message, is it waiting for a response? This could point to a problem with the communication? It can send but not receive.

(115200.8.N.1 and hardware flow control)

Karl

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[Chris Groenewegen]

But I do not change any settings and the other ROMs and Configurations work flawlessly hence my conclusion that it must be in the ROM or the logic IC's doing the address selection and paging.

On Monday, March 11, 2019 at 9:34:30 PM UTC+1, karlab wrote:

If the serial send out the message, is it waiting for a response? This could point to a problem with the communication? It can send but not receive.

(115200.8.N.1 and hardware flow control)

Karl

On 11 Mar 2019, at 21:19, Chris Groenewegen <cbj.gro...@gmail.com> wrote:

I'll try that another time. I just finished re-testing the Full CP/M kit and it was behaving intermittently. Only the message appears, via the serial terminal no the PI-Zero and then the whole thing hangs again. There must be something awkward still with the timings or perhaps a botched up ROM IC (from the KIT) although when reading it with the TL866 it seems fine. Perhaps the paging is still an issue and that could probably be related to the logic IC's on both the ROM and RAM board?

I can run it now per your configuration #2 here as per your suggestion. Plodding through still. Will keep you all posted. Regards, Chris

On Monday, March 11, 2019 at 9:05:36 PM UTC+1, karlab wrote:

Hi Chris

The pictures was taken from Steve’s documentation, and I just selected two of the many possible configurations.

I wasn’t sure what modules you had, try other configurations and other ROMs.

From SCMon you can page in and out memory, dump memory, start RAM test, start BASIC or CP/M and so on.

Karl

On 11 Mar 2019, at 20:08, Chris Groenewegen <cbj.gro...@gmail.com> wrote:

Your figure #1 is perfectly do-able. Your figure #2 not. I've seen those in the Small Computer Monitor manual but 2nd figure does not work for me. I'm missing the jumper/link yes or no indication on the RAMboard at the bottom btw. What also DOES work is the pageable ROM board with the normal original RAMboard in. I will re-test the workings with the different RAM ICs now but am puzzling to identify the root cause here.

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[Chris Groenewegen]

Hello Karl and RC2014 friends, it's on and off for me when I can spend time on the project. I've ordered some new logic IC's and have been playing around with the Small Computer Monitor. In the original CP/M ROM R0001009 it's running fine with the original RAM or the Pageable RAM with the lower RAM (62256) removed that is. I can not seem to get the full pageable 64Kram with the CP/M ROM working. So tips to back-track are really appreciated. 

Chris

On Monday, March 11, 2019 at 9:34:30 PM UTC+1, karlab wrote:

If the serial send out the message, is it waiting for a response? This could point to a problem with the communication? It can send but not receive.

(115200.8.N.1 and hardware flow control)

Karl

On 11 Mar 2019, at 21:19, Chris Groenewegen <cbj.gro...@gmail.com> wrote:

I'll try that another time. I just finished re-testing the Full CP/M kit and it was behaving intermittently. Only the message appears, via the serial terminal no the PI-Zero and then the whole thing hangs again. There must be something awkward still with the timings or perhaps a botched up ROM IC (from the KIT) although when reading it with the TL866 it seems fine. Perhaps the paging is still an issue and that could probably be related to the logic IC's on both the ROM and RAM board?

I can run it now per your configuration #2 here as per your suggestion. Plodding through still. Will keep you all posted. Regards, Chris

On Monday, March 11, 2019 at 9:05:36 PM UTC+1, karlab wrote:

Hi Chris

The pictures was taken from Steve’s documentation, and I just selected two of the many possible configurations.

I wasn’t sure what modules you had, try other configurations and other ROMs.

From SCMon you can page in and out memory, dump memory, start RAM test, start BASIC or CP/M and so on.

Karl

On 11 Mar 2019, at 20:08, Chris Groenewegen <cbj.gro...@gmail.com> wrote:

Your figure #1 is perfectly do-able. Your figure #2 not. I've seen those in the Small Computer Monitor manual but 2nd figure does not work for me. I'm missing the jumper/link yes or no indication on the RAMboard at the bottom btw. What also DOES work is the pageable ROM board with the normal original RAMboard in. I will re-test the workings with the different RAM ICs now but am puzzling to identify the root cause here.

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[karlab]

Hi Chris

So what you are saying that the system works when the lower RAM is removed, and when you insert the lower RAM it doesn't?

Have you tried to swap the two RAM chips? 

With SCMon, you can download RAM testing code (its part of the SCW package).

Then the third thing to check is the jumper settings on RAM and ROM boards, are they correct? 

I hoped Spencer would have removed these jumpers long time ago, it's just confusing.

If all is OK so far, then you have to consider the page switching mechanism.

With the pro kit the paging signal is transferred by the 4th pin on the extended part of the connector (need the Backplane Pro)

On the plus kit it is provided by a cable between the two points. 

If all connection is good you may have a problem with the glue logic on the RAM and ROM boards.

I have wired the  paging signal to U4, but it is also possible to use U1 to U3 pins, then I can use the modules with both single and double row female headers on the backplane.

Karl