To avoid entering in lvp mode by mistake at powering up, a pull down was used on PGM.
It was a long discussion on Microchip or piclist forum about using pickit2 in lvp mode (using aux output). On Wed 4 Jan 2023, 8:15 AM vsurducan <[email protected] wrote: > On old PiC16F877, entering in lvp mode hapened with a low to high > transition on LVP pin. I remember pull-up was used, but pull-down seems > also ok. > > On Tue 3 Jan 2023, 6:36 PM Rob CJ <[email protected] wrote: > >> Hi RobH, >> >> If the default of the samples (and user programs) would be to enable LVP >> then the warning comment should then be to have a pull-up resistor on the >> PGM pin or am I interpreting the datasheet wrong? >> >> Kind regards, >> >> Rob >> >> ------------------------------ >> *Van:* [email protected] <[email protected]> namens Rob >> Hamerling <[email protected]> >> *Verzonden:* dinsdag 3 januari 2023 16:59 >> *Aan:* [email protected] <[email protected]> >> *Onderwerp:* Re: [jallib] USB_help >> >> >> Hi RobJ, >> >> On 03/01/2023 15.33, [email protected] wrote: >> >> >> I had an e-mail discussion with the other Rob since he also had >> programming issues using LVP. It seems that for some (older?) PICs that >> have LVP only work if you pull a special PGM pin high (so not floating) >> with a resistor. >> >> >> I'm afraid I have to correct this: When LVP is enabled and the PIC has a >> Pin_PGM, this pin requires a *pull_down* resistor to prevent the PIC >> entering LVP mode accidentally. >> >> In order to prevent issues I could check which PICs have this PGM pin and >> for those PICs create only blink samples with LVP disabled. Another option >> is to enable LVP and mention in the blink sample comment to pull the PGM >> pin high for those PICs. >> >> >> The *pull-down* requirement applies to every program, not only samples >> also user programs. >> >> The reason (at least one of 'm) to specify LVP ENABLE in Jallib (blink) >> samples was that it allows the use the Microchip SNAP programmer (or any >> other LVP programmer) besides any HVP programmer like PicKit3. So my vote >> would be for adding a warning comment. >> >> Regards, Rob. >> >> >> -- >> *Rob H*amerling, Vianen, NL >> >> -- >> You received this message because you are subscribed to the Google Groups >> "jallib" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/jallib/bcc403f2-6580-1d18-0d8a-25109e7a933d%40gmail.com >> <https://groups.google.com/d/msgid/jallib/bcc403f2-6580-1d18-0d8a-25109e7a933d%40gmail.com?utm_medium=email&utm_source=footer> >> . >> >> -- >> You received this message because you are subscribed to the Google Groups >> "jallib" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/jallib/GVXP195MB1637E54549EBC46A30C7266AE6F49%40GVXP195MB1637.EURP195.PROD.OUTLOOK.COM >> <https://groups.google.com/d/msgid/jallib/GVXP195MB1637E54549EBC46A30C7266AE6F49%40GVXP195MB1637.EURP195.PROD.OUTLOOK.COM?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "jallib" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/jallib/CAM%2Bj4qvc5FJ%2BA9eVpwjG6K13FxzF%3Dsukai%3D%3DvUuPSEHTfH18_Q%40mail.gmail.com.
