Post by thread:Help these pic16c74's are not erasing! (using ITU

I recently started working with pic16c74's. I bought a dataerase II from digikey with the timer. I thought spending $50 would buy a quality UV source. It takes atleast two 10 minute cycles to erase. But sometimes, it takes 5-6 times (1hour), when there are stubborn bits. My ITU programmer also makes things difficult. I try to check the contents of the program memory before programming them to make sure they are fully erased. From looking at the data file, they all look erased but it doesn't always work that way. Then I reprogram and the I get a message that programming failed and then I have to my pics fully erased. I have 4 on hand and they all have the same problem. I also make sure that I DO NOT set the code protect bit, which I was told contributes to long erasure times. Does anyone have any advice to rectify this problem. I have no problems with my 16c61 pics. They take only 4 minutes. Does the dataerase uv bulb degrade over time. I have had it only a few weeks. I wish Microchip would convert all of their erasable pics to EEPROM. This would solve a big problem. [EOB]

>I recently started working with pic16c74's. I bought a dataerase II >from digikey with the timer. I thought spending $50 would buy a quality UV >source. It takes atleast two 10 minute cycles to erase. But sometimes, it >takes 5-6 times (1hour), when there are stubborn bits. My ITU programmer also >makes things difficult. I try to check the contents of the program memory >before programming them to make sure they are fully erased. From looking at >the data file, they all look erased but it doesn't always work that way. Then >I reprogram and the I get a message that programming failed and then I have to >my pics fully erased. I have 4 on hand and they all have the same problem. I >also make sure that I DO NOT set the code protect bit, which I was told >contributes to long erasure times. Does anyone have any advice to rectify this >problem. I have no problems with my 16c61 pics. They take only 4 minutes. >Does the dataerase uv bulb degrade over time. I have had it only a few weeks. >I wish Microchip would convert all of their erasable pics to EEPROM. This >would solve a big problem. > >[EOB] > Neil, You are right, the erase times are very long and not what is to be expected. Somethings to consider: The eraser is dodgy and the UV output is below normal or varies for erasure to erasure. The ITU programmer is {sometimes?] over programming the PICS. This will make the 17C74 take longer to erase. Because the 16C61s erase much quicker anyway, you may not notice this happening with these chips. It is normal for any 5V only programmer to occasionally "LIE" about a device being fully erased. This occurs when the some device cells are right on the "erase margin." When the device is programmed, and with changes in temperture, the margin can shift and the programmer then sees the partially erased bits it missed before. I think you need to cross check with someones else's eraser and/or programmer. -Jim

Jim Robertson <spam_OUTPICLISTTakeThisOuTMITVMA.MIT.EDU> wrote: > [Quoting Neil Gandler:] > > It takes atleast two 10 minute cycles to erase. > > But sometimes, it takes 5-6 times (1hour) > > I think you need to cross check with someones else's eraser and/or > programmer. Neil: I have one of those Daterase-II erasers... My experience with 16C74s is similar to yours. I also have a couple-hundred-dollar Spectraline eraser... It takes even longer. Two things may help: 1. Cover the PIC's window with an opaque label while you're programming... It seems that the chips require more programming pulses when the window's exposed to light. I have nothing except empirical evidence to support this theory, and my samples are statistically small, but it can't hurt. 2. Make sure that you've removed ALL the adhesive residue from those labels before you put the chips in the eraser. -Andy Andrew Warren - .....fastfwdKILLspam@spam@ix.netcom.com Fast Forward Engineering, Vista, California http://www.geocities.com/SiliconValley/2499