Mike's PCjr Page

Hello,

I am new to EPROM programming and am hoping for some information to successfully program ATMEL AT27C256R / AT28C256 chips being used for IBM PCJR ROMS.
I have assembled cartridge kits, purchased Atmel chips, and a GQ-4x4 programmer.
There are several options to select when writing a chip.
Can you tell me the proper settings below for writing the JR rom images?
Appreciate your response here. I've researched this online but have not been able to find the information.

Read Mode-
Normal
Even Byte
Odd Byte
1st Byte of 4
2nd Byte of 4
3rd Byte of 4
4th Byte of 4
1st 2 Byte of 4
2nd 2 Byte of 4

Fill Mode-
Normal
Fill 'FF'
Fill '00'

File Offset - 000000

Device Offset - 000000

Speed
-2
-1
0
1
2




Thanks in advance,
Sonny

I'd say use Normal wherever you can. This is a single ROM image inside a single EEPROM, so there's no need to do any of the even/odd/first byte of n options, those would be used when there is a large amount of data spread across multiple chips.

Unused bytes in an EEPROM should be FF which is the erased state, so if the burner is "filling" in unused bytes to write the entire EEPROM size, you can set that to FF. No idea what a "Normal" write would be! It likely won't matter at all what this is set to.

I'd say Offsets should be 0 since you're bin file is already exactly 8k (or whatever it is) and you want it to start at the beginning of the EEPROM's address space.

Speed is determined by how fast the programmer is throwing data to the EEPROM, so start with 0 and if you get compare errors, try slowing it down with -1 or -2.

I've never used that burner before, so these are semi-educated guesses.

I also assume you've stripped any header info out of the .bin file already. Your bin file should start with 0x55 0xAA as the first 2 bytes of the file.