anyone want to test my 27c020 eproms?

coinheaven · Post by **coinheaven** » Sat Feb 03, 2007 6:01 am

so i have about 20+ of these eproms that are verified as erased on my willem eprom programmer, but they wont program for some unknown reason. i have no clue what to do. does anyone want to test out 2 of these for me and tell me what i am doing wrong? i will send out 2 erased chips to someone and they can keep the chips, i just want to know what is wrong.

blargg · Post by **blargg** » Sat Feb 03, 2007 8:34 am

Maybe some of the bits can't be set to 0 (programmed). See what reads back when you try to program all data with zeros.

coinheaven · Post by **coinheaven** » Sat Feb 03, 2007 9:31 am

how do i do that?

blargg · Post by **blargg** » Sat Feb 03, 2007 10:52 am

Prepare a file of all zero bytes and write this to the chip, then have the programmer dump the contents back to the PC. Verify that the data read back is the full size of the chip, and all zero.

coinheaven · Post by **coinheaven** » Sun Feb 04, 2007 6:03 am

ok, i dont know how to make a file of all zero bytes and i never dumped a file back onto the pc from a chip, any help on this would be great. also, what is this testing for?

blargg · Post by **blargg** » Sun Feb 04, 2007 11:57 am

An EPROM is composed of many bits that can be programmed to zero or one. You said that you verified that it was erased (all bits set to 1), therefore it appeared OK, but you couldn't successfully program it. My idea is that all bits in the erased state is no guarantee that they can all be programmed to 0, so you might also try setting them all to 0 and verifying that, in case any were "stuck" (sort of like bad pixels in LCD screens).

As for making a file of all zero bytes, I suggest you look into basic file editing tools and how data is stored in a computer system. Read up on hex editors.

teaguecl · Post by **teaguecl** » Sun Feb 04, 2007 1:35 pm

coinheaven wrote:ok, i dont know how to make a file of all zero bytes and i never dumped a file back onto the pc from a chip, any help on this would be great. also, what is this testing for?

It sounds like you're not quite sure how to operate your programmer's software. What software are you using? How do you know your chips are erased? How do you know the programming of them is failing?
Also, from a unix prompt you can create a 256KB file of zeros with:

Code: Select all

dd if=/dev/zero of=test.bin bs=1024 count=256

That is the easy way. If you are on a DOS based system, just get a hex editor and open a new file, and start typing 00's. After you have a few, start copying and pasting it repeatedly until you get up to 256KB's worth.

leonk · Post by **leonk** » Sun Feb 04, 2007 4:11 pm

Coin, what Willem Programmer are you using? I know the USB ones are HORRIFIC! Lots of talk about this over on willem.org forum.

These kind of EPROMs must be verified that they are empty at 4.5v and programmed at ~6.5v (they operate at 5v). There are no willem programmers that can go down to 4.5v to do an accurate empty verification, and the USB ones only program at 5V!

Lastly, I hear the software has a build in tester. Set the pins as seen in the test H/W tab of the programming software. Then check all of them. Lastly, using a volt meter, check the voltage between ground (pin 16) and each one of the pins. They should all have a voltage!!

If you find any pins with 0v, that means the programmer is broken. (e.g. bad dip switch, bad logic ic, etc).

These willem programmers do work, but you really need to know how to fix them in order to maintain them.

albailey · Post by **albailey** » Mon Feb 05, 2007 8:41 am

I know that my Willem (Dual powered) wont program my PM29F002 Flash chips. (which is the same size as what you are trying, just a different setup)

The response on willem board was that I must have a bad chip. I tried a dozen chips and none of em worked so I'm more inclined to blame the programmer or its software. I also bought an external power supply and still no good. I had no problem with other (smaller) chips.

If anyone would like to suggest a good programmer for NES homebrew, I'd love to hear it. (EPROMS and Flash) I dont mind paying more for a good one.

Al

rbudrick · Post by **rbudrick** » Mon Feb 05, 2007 8:46 am

256KB=262144bytes

262144 bytes x 8=2097152 bits.

So, make a file with 2097152 zeroes. Copying and pasting is your friend.

I had to do this to make blank FDS images recently.

-Rob

leonk · Post by **leonk** » Mon Feb 05, 2007 10:07 am

albailey wrote:I know that my Willem (Dual powered) wont program my PM29F002 Flash chips. (which is the same size as what you are trying, just a different setup)

The response on willem board was that I must have a bad chip. I tried a dozen chips and none of em worked so I'm more inclined to blame the programmer or its software. I also bought an external power supply and still no good. I had no problem with other (smaller) chips.

If anyone would like to suggest a good programmer for NES homebrew, I'd love to hear it. (EPROMS and Flash) I dont mind paying more for a good one.

Al

Did you test your programmer using a voltmeter and built-in test function? Good willem programmers have all their IC's socketed. One of them might have gone bad on you.

blargg · Post by **blargg** » Mon Feb 05, 2007 10:50 am

So, make a file with 2097152 zeroes. Copying and pasting is your friend.

I kind of figured that you could just use a one-byte file and let the programmer mirror it, as I figure it has an option to do.

coinheaven · Post by **coinheaven** » Mon Feb 05, 2007 11:09 am

leonk wrote:Coin, what Willem Programmer are you using? I know the USB ones are HORRIFIC! Lots of talk about this over on willem.org forum.

These kind of EPROMs must be verified that they are empty at 4.5v and programmed at ~6.5v (they operate at 5v). There are no willem programmers that can go down to 4.5v to do an accurate empty verification, and the USB ones only program at 5V!

Lastly, I hear the software has a build in tester. Set the pins as seen in the test H/W tab of the programming software. Then check all of them. Lastly, using a volt meter, check the voltage between ground (pin 16) and each one of the pins. They should all have a voltage!!

If you find any pins with 0v, that means the programmer is broken. (e.g. bad dip switch, bad logic ic, etc).

These willem programmers do work, but you really need to know how to fix them in order to maintain them.

I programmed other 27c020 chips ok, so i think the programmer is fine. So your saying that the chips might not be empty because the programmer cant do an accurate empty verification. Maybe i should erase them longer.

albailey · Post by **albailey** » Mon Feb 05, 2007 11:45 am

leonk wrote:
albailey wrote:I know that my Willem (Dual powered) wont program my PM29F002 Flash chips. (which is the same size as what you are trying, just a different setup)

The response on willem board was that I must have a bad chip. I tried a dozen chips and none of em worked so I'm more inclined to blame the programmer or its software. I also bought an external power supply and still no good. I had no problem with other (smaller) chips.

If anyone would like to suggest a good programmer for NES homebrew, I'd love to hear it. (EPROMS and Flash) I dont mind paying more for a good one.

Al
Did you test your programmer using a voltmeter and built-in test function? Good willem programmers have all their IC's socketed. One of them might have gone bad on you.

I didnt try running any diagnostics. I'll give that a shot.

coinheaven · Post by **coinheaven** » Fri Feb 09, 2007 6:52 am

the offer is still open, if someone thinks they can figure out the problem. i have been swamped at work and havent had time to mess around with them.