• Please review our updated Terms and Rules here

How to dump Tandy 1100 Character rom via software?

A

acadiel

Experienced Member
Joined
Dec 19, 2009
Messages
287
Trying to figure out if there’s a way to dump this via software so I can get it to the MESS folks. This is the 1100 character rom. I’d rather only desolder it as a last ditch effort (I’d have to pry the label off and figure out what kind of chip it is, too.)

Any thoughts?
Thanks!
 

Attachments

  • EBBBCFFD-35EC-45F1-AAC1-285523B1B4C8.jpeg
    EBBBCFFD-35EC-45F1-AAC1-285523B1B4C8.jpeg
    642.2 KB · Views: 14
Character ROMs in this generation of display hardware are normally not mapped to the system's address space, so chances are it can't be dumped in software.
 
I agree, the character generator is usually part of the circuitry that is not generally available to the CPU.

However, if the ROM is soldered into the circuit, it is possible to still acquire the contents if you have access to something like a logic analyser.

By writing the characters $00 to $FF into the video RAM (by the CPU) and then storing the data output from the ROM, it should be possible to work out what the ROM contents are.

You will need some means of determining a synchronisation point. This assumes that there are no ‘additional’ character sets within the ROM that can be separately enabled (e.g. by an I/O port bit). You can determine this from the size of the EPROM part itself and the user manual.

You can also do it in a slower manner. For example, write the character ‘A’ to all of the VDU screen memory and capture the character generator ROM data output. The ROM data output should constantly cycle around all of the rows of the letter ‘A’.

Of course, you could also just look at the ‘bits’ on the screen...

If you want to map the ROM data and address, you will also need to look at the ROMs address bus - either separately or at the same time as the data.

If any of this sounds of interest to you, we could perhaps work up a procedure based upon what test equipment you have available to you.

I see from a search that you have been trying to track down technical information for this machine fir a while?

Dave
 
Hi, @daver2 !

Yes, I've been working to try and compile any information on this as well as the Panasonic BP150 (it's sibling). I've been able to dump the option ROM and BIOS of both the 1100 and BP150 (the main difference between the two is Deskmate is on the Tandy and misc utilities are on the BP150). The character ROM is the last part for me to get a complete set to the MAME folks so they can accurately emulate the fonts.

I really don't have much in ways of test equipment. I may have some 28 pin EPROM test adapters (the kind you can put the probes on the top), and I have a couple of standard EPROM programmers, but I don't have an oscilloscope. I do have an industrial Hakko desoldering tool, but I'd really have to figure out what kind of chip this is and if I have to remap the pinout to dump it with an EPROM programmer. To do that, I'd potentially have to damage the label on the chip.

Some of your other points -

The technical manual is lost still until we find it somewhere (it WAS released - I've emailed the only person on the web who said he had one, and he's not sure if he even still has it.)

The system has a truncated (50 pin?) ISA slot onboard - and it's got potential to have someone build an XTIDE and/or EMS/RAM disk cards to go into it. Until we get the pinout, we can't do anything with it. (Wouldn't it be GREAT to have a drive in these things??) [As an aside, the 1100HD - has a slightly different BIOS which I haven't dumped - it supports a MFM 20/40MB XTA drive, and has this instead of the truncated ISA slot.]

The floppy drive only supports one drive channel - and I've been able to fix some of the belt driven drives by putting new belts, and also have gotten a GoTek to work with an adapter.

Here's the truncated ISA slot, BTW, as well as the super rare EMS RAM card:
1645203633016.png
ems1.jpg

ems2.jpg
ems3.jpg
 
You must log in or register to reply here.
Back
Top