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 Using The Enhanced/Dual power Willem Programmer
 Inconsistent Reads with 2732 EPROM

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T O P I C    R E V I E W
slipnfall Posted - 02/15/2006 : 22:09:39
Hi Folks,
Just a little problem here: I'm trying to read a 2732 UV EPROM on the Enhanced Willems programmer(that's sold on Ebay). Hardware test passes, LPT1 set to ECP+EPP. I have verified I/O and Vpp signals with a DMM. I can not get consistent reads from the PROM... if I watch a particular address in the buffer, and do multiple reads, one or two bits will change every 6-7 read. I attempted to extend the timing sliders, but the data changed drastically. Can anyone explain what parameters these two sliders refer to? Are the read/write setup or hold times?

I have unjumpered the safety, and Special Chip is selected for 2732.

I am a little confused about the PCB3 and Willems button: does the button *display* the mode it's in, or do you click the particular mode to go to that mode? Hope this makes sense... in other words, if it says 'Willem', does that mean I'm *in* Willem mode, or click there to select that mode?

Thanks folks! I hope to have some 29FS512s to play around with this week.

'slip
4   L A T E S T    R E P L I E S    (Newest First)
slipnfall Posted - 02/17/2006 : 07:36:02
Hi Dennis,
I see - I guess I was just too haste on my purchase. I was speculative about the power arrangements, but figured if they could handle the Vpp(boosting I mean), the Vcc was a given. Anyways, I would normally be inclined to modify the board to work for me, but for some reason I just don't want to mess with this board. I very much appreciate your offer, and will likely take you up on that. I'll root around for your email: if you don't hear from my today ,shoot one to *erased*

Respectfully,
Jamie
DL Posted - 02/16/2006 : 21:48:29
Hi,

For 2732, the voltage drop is coming from at least two places. The transistor used to switch VCC to the programming sockets, and the circuitry used to route power to pin 28 on the ZIF socket. Most programmers use a jumper, so the same voltage appearing on pins 30 and 32 of the socket would appear on pin28. The enhanced universal programmer is "broken" for DIP24 devices; eventhough it has options for 2732, 2716, and 2816...

Some have addressed the power at pin28 problem on that design with a jumper to pin 32. If you eliminate the voltage drop in the transistor used to switch VCC to the programming sockets, you might be able to read. I say might because, as you pointed out, USB devices are only guaranteed 100mA of current at 4.5-5.5V. Any device drawing more must negotiate with the USB controller for up to 500mA. Whoever started powering boards from USB was ignorant of this requirement. Obviously there's no intelligence on the programmer and it will try to take whatever it wants. This can starve other devices on the BUS for power and can burn up the USB controller.

The good news is that your 16bit adapter will work with any Willem based programmer. Providing you take care of the voltage drop problem that affects virtually all of them. The only programmer I'm aware of that handles this well is the Willem 4.1. It's a new design with a relay (my idea) and only available from Willem for the past few months.

I'm sure it will only be a matter of time before the new features are cloned. But for the time being, they're only available from Willem.

If you're in North America, I'll consider taking your enhanced programmer in trade. But I can't offer anything near what you paid, but at least you'll have a programmer that will work for 2732. You'll still want to modify it to give you more VCC options so you can do programming and blank verification at the correct voltages. Once you've programmed an EPROM correctly, it doesn't matter what voltage you read it at; as long as it's within specs for the device.

I'm selling Willem's 4.0, 4.1, and 4.5; though the 4.0 is now obsolete.

HTH,
Dennis
slipnfall Posted - 02/16/2006 : 14:01:30
Thanks for the response. Wow, what a dissapointment... I paid $65 for this plus a 16-bit eprom adaptor... You were correct - with Vin of 4.98, Vcc was 2.89V! You mention voltage drops - do you know where these occur? Also could it be a matter of current limiting on the USB port? IIRC it can only draw a max of 4-500mA, but must *request* that ammount, nominal is like 100mA.

I am really unhappy with the quality of this board in general... poor solder joints, some not even soldered, lots of solder flux, and worst of all, scraped chips...I wish their return policy was a little more fair.
DL Posted - 02/16/2006 : 11:22:15
Hi 'slip,

The enhanced universal programmer does not support EPROMs well. It's marginal for CMOS EPROMs and will not work for NMOS. It also does not work for DIP24 devices; which includes 2732, 2716, 2816. Eventhough you have options for those devices, power routing for DIP24 devices is broken and you'll have too much voltage drop. If you measure VCC at pin24 on the 2732 while reading, you'll see that it is significantly below 4.5V. That is the lowest voltage that you can read a 2732. The lowest voltage that you should program a 2732 is VCC=6V. Obviously the enhanced universal programmer can't do this. Additionally, the USB spec says that the 5V supply can be 4.5-5.5V (10% tolerance). If it's on the low end, you get even lower voltages to your device.

Some have considered hacking up a USB cable to provide higher voltage to the board. You can only do 5.25-5.5V safely. Some of those designs use 74HCT logic that requires VCC=4.5-5.5. The PAL chip will probably be the limiter. I haven't checked it's VCC spec, but it'll either be 4.5-5.5 or 4.75-5.25.

If you're going to be programming EPROMs, buy a more appropriate programmer. I recommend the Willem 4.1; it fixes the voltage drop problem and is easily modified to obtain higher VCC voltages. Schematic and component diagrams are available, and support is very good (on willem.org).

HTH,
Dennis

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