RC2014 PRO ROM Module

[Paul Bigwood]

Hi, Further to my earlier post I am now looking for more information on the ROM board that was supplied with the kit.

The board is described as the Pageable ROM and has a 32 pin socket. The ROM position is silk printed SST39SF040 /020/ 010 and the 32 pin ROM supplied is labelled 24886009.

I’m wanting to use the SCM monitor in Page 8 so set A15/14/13 jumpers to 1 A10/11/12 open and the Page jumpers to 00111 for 8K page.

Doesnt boot so decided to try the Mini ROM which is a 27C512 and labelled R0000009, so has the SCM monitor in Page 8. 

Problem is that Pin 30 ( pin 28 on the 27C512) is grounded? so no 5V to the Chip. 

Removed all chips and jumpers and the pin is definitely shorted, close examination of the board doenst show any visible shorts, so must be under a chip socket 

Is there a board layout available for this particular board that can help me find where the likely short is?

Any pointers appreciated 

Paul 

[Jon Jones]

https://rc2014.co.uk/modules/pageable-rom/

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[Paul Bigwood]

Thanks Jon,

I’ve seen that but it doesnt cover the 32 pin socket design that my board has.  

i think Spencer has updated the design. I have searched github but not found it yet. 

I’ll post a picture of the board if I can work out how to do it on Google groups.

BR Paul 

[Jon Jones]

Spencer does post in these groups. He's been offline the past week or so, so it might be a few days until he's caught up and spots this to give an authoritative answer.

J.

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[Spencer]

Hi Paul, Jon,

Yeah, I'm still keeping a low profile until I have got all my EMF Camp unpacking done and cleared the backlog of orders. I've only skimmed the messages so far, but hopefully I can point you in the right direction.

So, unfortunately the schematic for the current Pageable ROM Module does not exist anywhere. Originally this board was designed for the 27C512 chip, but during the global chip shortage, this was unavailable. A KiCad upgrade had garbled my original schematic too. However, the 27C512 and 39SF010 have got almost identical pinouts if you ignore the top 4 pins on the '010, and move VCC. So the change was made directly to the PCB file without a schematic.

You are right that Pin 30 is connected to ground, so this means that a 27C512 won't work. Bending that pin out and attaching it to 5v will fix that, but then you'll have trouble getting that back in your RC2014 Mini.

The address, data, and chip enable lines are all as before, so the jumpers to set the ROM bank and everything else about the schematic is identical.

With regard to getting the RC2014 Pro tested with the RC2014 Mini as a known good starting point, your strategy of removing a chip from the Mini and putting in the corresponding module from the Pro is sound. None of the Enhanced Bus pins will matter, although on the RAM module you will need to set the jumpers to start at 0x4000 (from the top, jumpers left, left, right, left) so that it doesn't clash with the ROM. As you say, SCM (ROM image 9) will work with either UART, and is present on both the Mini and the Pro.

Hopefully that helps. I'll keep an eye on this thread in case there's anything else.

Cheers

Spencer

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[Paul Bigwood]

Hi Spencer,

Thanks for the update. I understand the logic now. Bending Pin 28 on a 27C512 spare ROM Copy will enable me to test the ROM board on the mini board. Since my SMBaker SIO board worked plugged into the mini with the 68C50 unplugged I can test the PRO SIO board as well and do the same with the RAM board. Thinking about it removing the CPU and plugging the CPU card in would also test the CPU card. The clock and reset board worked in the 8 plane backplane so they are OK. At least this way I have verified the basic individual boards. Then its get it working on the backplane and then CPM.

Steve's SCM is really good for testing especially the 'any ram, any uart'  version. 

Best Regards 

Paul 

[Spencer]

Yes, that should narrow things down to a specific module. (or if every module checks out ok, then it's the backplane.)

Another trick that SCM has up its sleeve is to run a moving dot display on Port 0. So if you have a Digital I/O Module, then even without a working serial module you can see the dot run along the LEDs which confirms the clock, CPU, ROM and RAM have minimal funtionality at least.

Spencer

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