ROM section of a 6801U4 MCU

[Stefan Nordkvist]

Posted on March 28, 2018 at 14:26

Hi!

I wonder how one is to specify the ROM contents of a legacy MCU.

The MCU in question is the 6801U4 since long discontinued..

Does anyone know if the ROM section is OTP or can it be erased/reprogrammed?

And If I have a blank one, how can I program that part? (if possible)

Thank you!

#6801u4 #legacy-mcus #6801 #ef6801u4

[Tesla DeLorean]

Posted on March 28, 2018 at 14:51

Isn't that a Motorola(Freescale) part? Or do you have some SGS-Thomson (ST) part in mind?

Some have 6K ROM, custom ones would have ROM mask defined by customer .HEX file

Look for 'Universal Programmers' from the era to see if any of those provided support for the part.

Most parts like that from the 1980's would have user code in external EPROM. Anyway start by finding a Data Sheet or Data Book (likely to be physical, or scanned, than searchable PDF)

[Stefan Nordkvist]

Posted on March 28, 2018 at 15:03

Hello!

This is the part i have in mind. The datasheet didnt help much thou, just that the customer needs to contact them and sending eproms or disks with the correct ROM code marked with wich adress space they belong to :/. I would like to be able to program the 6801u4 mcus with the original 4k ROM somehow, if its possible.

I wonder if there are any other legacy mcu who works the same in this family except it has the rom external?? That would make the whole thing a bit easier.. 

EF6801U4 and MC6801U4 are the same i suppose?

http://www.bg-electronics.de/datenblaetter/Schaltkreise/EF6801.pdf

 

http://rpm.planetaclix.pt/ecu/MC6803U4.pdf

 

https://www.computer.org/csdl/proceedings/afips/1982/5089/00/50890067.pdf

 

EDIT: AH.. think I just answered my own question.. the MC68701U4 is the Eprom version and the MC6801U4 is the ROM version! lol..

'MC68701 U4 is pin and code compatible with the MC6801 U4 and can be used to emulate the MC6801 U4, allowing easy software development using the on-chip EPROM. Software developed using the MC68701 U4 can then be masked into the MC6801U4 ROM. In order to support the on-chip EPROM, the MC68701U4 differs from the MC6801 U4 as follows:

(1) Mode 0 in the MC6801 U4 is a test mode only, while in the MC68701 U4 mode 0 is also used to program the on-chip EPROM.

(2) The MC68701U4 RAM/EPROM control register has two bits used to control the EPROM in mode 0 that are not defined in the MC6801 U4 RAM control register.

(3) The RESET /Vpp pin in the MC68701 U4 is dual purpose, used to supply EPROM power as well as to reset the device; while in the MC6801 U4 the pin is called RESET and is used only to reset the device.'

[Tesla DeLorean]

Posted on March 28, 2018 at 16:56

My expectation is that the EPROM device would be up in the 21.5V range, certainly a lot of the newer/cheaper programmers wouldn't get there. Would also expect the presence of security fuses, and a difficulty in executing or extracting code from a ROM device. This stuff would be pre-JTAG, but might have scan chains for test modes.

eBay is a good source for vintage equipment, but it's likely to need older PC/AT computers running at lower speeds with DOS, requiring parallel ports or custom ISA cards. Stand-alone things like Dataman's Softy might still be floating around, as well as Motorola Exorciser equipment.

http://www.vcfed.org/forum/showthread.php?52632-Reading-an-MC68701

 

[Stefan Nordkvist]

Posted on March 28, 2018 at 17:15

Yeah but I don't need to read it, only write to it . I have a old advantech uxp-48 that should do the trick..