Unexpected addresses viewable using the DUMP command

[Guest]

Hi guys,

Apologies for the odd question. I'm a complete beginner to EPROMS and programming in general. I'm jumping in the deep end so I can update the firmware in some moving lights using data files from the manufacturers website.

I've just received my secondhand S4 and am in the process of playing. S4 has Library 2.93 with 128kB of RAM.

To test I have a 27C256B in the ZIF (an original chip programmed by the manufacturer of the moving light). FUNC-PROM correctly identifies the chip. I can LOAD (00000-07FFF) into the S4. Both the PROM and the S4 then have matching CheckSums for the loaded address range.

However... if I then DUMP the PROM to the screen, using the Up-Arrow I can view the contents of addresses up to 0FFFF. I was under the impression that this was the final addresses of a 64kB chip. But the 27C256B is a 32kB chip... I'm a bit confused. The last few dozen bytes just contain a copyright notice from the manufacturer of the moving light. Everything else before that (before I got bored) look like they contain unblown FF's.

So... any ideas, and do I even need to worry about it? Just waiting for my EPROM eraser to be delivered so I can start writing the updates.

Thanks

Steve

[Dataman (Neil Parker)]

Hi Steve,

Welcome to the world of memory device programming.

The S4 DUMP command will show you the range up to 0FFFFh regardless of the device selected. This is nothing to worry about as the valid address range for the device will contain the expected data. I guess this is a bug of sorts.

Good luck with your memory programming.

Neil

[Guest]

Thanks for the reply Neil.

I think what's confusing me most is that the data from 0FFE0 to 0FFFF is recognisable. It's a short copyright notice from the lighting manufacturer.

Steve