Hi all,
I recently finished building a parallel port programmer and have been playing around with a 16F877-04P. All was well at first but as time passed I started to get verification errors while programming the chip, increasing in frequency until it has now reached the stage where I can't program it successfully anymore. Browsing through this forum I've now eliminated the PC, parallel port cable, programmer software and programmer voltages.
WinPic800 reports random addresses, 0862h, 0882h, 08F2h, 0902h, 0a12h and 0a39h at fault. When I read back the contents of the chip the reported address has the correct value but of course programming did not commence beyond that address. If I program the chip completely without verification then lots of addresses have bits cleared in them. If I fill the entire code range with bit patterns such as 1555h and 2aaah then programming and verification is successful.
I've now accepted that the chip is probably faulty is some way but would very much like to know what could've caused the problem so that I can prevent a reoccurence. Known mishaps with this chip is that I once programmed it as a 16F877A and today I discovered that I wasn't using a 4 MHz crystal in its test cicuit but a 20 MHz one. Not that it was protesting about it at the time.
Can anybody throw some light on the subject?
Regards,
Peter.
I recently finished building a parallel port programmer and have been playing around with a 16F877-04P. All was well at first but as time passed I started to get verification errors while programming the chip, increasing in frequency until it has now reached the stage where I can't program it successfully anymore. Browsing through this forum I've now eliminated the PC, parallel port cable, programmer software and programmer voltages.
WinPic800 reports random addresses, 0862h, 0882h, 08F2h, 0902h, 0a12h and 0a39h at fault. When I read back the contents of the chip the reported address has the correct value but of course programming did not commence beyond that address. If I program the chip completely without verification then lots of addresses have bits cleared in them. If I fill the entire code range with bit patterns such as 1555h and 2aaah then programming and verification is successful.
I've now accepted that the chip is probably faulty is some way but would very much like to know what could've caused the problem so that I can prevent a reoccurence. Known mishaps with this chip is that I once programmed it as a 16F877A and today I discovered that I wasn't using a 4 MHz crystal in its test cicuit but a 20 MHz one. Not that it was protesting about it at the time.
Can anybody throw some light on the subject?
Regards,
Peter.