Reading a ROM

[Dave Frederickson]

Can an EPROM programmer read a ROM?

Sounds like a simple question, but maybe it isn't.

Here's an example:
Suppose I'd like to copy a 128k-byte ROM for a Portable PLUS. This ROM comes in a 28-pin DIP package, however, the largest EPROM in a 28-pin DIP package is only 64k-bytes.

So how is the ROM read?

Dave

[Garth Wilson]

Programmers have to be able to read an ((E)E)PROM even to verify that that the programming "took." They can also read one in order to copy it, or to see if the contents match a particular image. So the answer is yes, and the driver software can give you files in various formats, showing the contents. A few of the many formats are Intel Hex, Motorola S-Record, and binary. http://srecord.sourceforge.net/ lets you convert between file types.

[Dave Frederickson]

I'm sorry, I meant mask-programmable ROM's like the Toshiba TC531000.
http://www.citylan.it/wiki/images/2/26/Tc531000.pdf

Because it's not an EPROM, programmers can't be configured to read it.

Dave

[cruff]

As long as the pin out is compatible with the programmer, and it knows the correct type of device, it should be doable. Most programmers should have a list of supported device types, which may be (mask) ROM, PROM, EPROM, etc.

[Dave Frederickson]

Seems I'm not the only one with this issue, but their solution requires an adapter.
https://forums.arcade-museum.com/threads...es.332492/

As my situation applies specifically to the Portable PLUS, using VGER to create a ROM image seems feasible, but I don't think VGER supports 64k-byte or larger EPROM's.
http://www.jeffcalc.hp41.eu/hpplus/files/vger.pdf

Dave

[Martin Hepperle]

Dave,

when the software was developed, EPROMs larger than 32 KB were probably not yet available.

A 64KB EPROM (27C512) is possible without problems.

You would configure a half bank with
EDISK.SYS /2 /H
to create a .HAF file with 63488 bytes on ram drive D: or e:

With two 64 KB EPROMS in a full-bank configuration you can thus store a directory with up to almost 128 KB data.
EDISK.SYS /2 /F
would make a set of EVN and ODD files on ram drive D: with a combined capacity of 129024 bytes.

128 KB per EPROM is only possible with some adapter - the Personal Software solution was to solder PLCC EPROMs onto a carrier PCB and use some jumpers and wires to switch between programming and operation modes.

Some EPROM software/burner combinations can read ROMs too, but not necessarily. One would possibly also need an adapter. and, please avoid feeding the high programming voltage to a ROM. The 12 V level may also be used to read the manufacturer ID from an EPROM, so one should switch this option OFF when trying to read a ROM as EPROM (or read as a generic EPROM).


Martin

[Dave Frederickson]

Hi Martin,

Thanks, I'm familiar with the VGER tools.

It's just that there exists a copy of Turbo Pascal 3.01A for MS-DOS on a single 27C512 and I can't figure out how it was created.

Dave

[Martin Hepperle]

Dave,

some months ago I have created this image following the VGER tools as per manual - what is the problem?

From my writeup:

Creating the EPROM Image Files
After having set up the files on D:, the IMAGE program is used to generate the required EPROM binary image file(s). Each image file can then be burned with any EPROM burner.

MARK
ROMNAME name this will become the name of the directory on B:
OEMNAME name typically a company or project name
FENCE
CHECKSUM adds the checksum(s) to the ROM images
SAVE /hh name writes the given number of Kbytes (hh in HEX) to the image file(s)
QUIT
Table 4 Minimum sequence of IMAGE commands.


In this case, /hh is /40

Martin