i put a MCP130T-450I/TT reset chip in a design, 'just in case' as the PIC reset line (MCLR) clears a lot of other things too in a fairly busy system
(this is different project from the other one i have been chattering about)
when i fired up the hardware i could not program the chip ("target device does not match"),
I 'scoped VPP and saw it was getting clipped, pulled the reset chip and then it programmed fine
so three related questions:
1] i inherited a 0.1uF cap on the MCLR line and i left it in, are the any worries about it slowing down VPP as i notice VPP is pulsing during programming, it seems to work ok, just looking for input from others on this (using MEL U2 programmer)
2] the reset chip is open drain with an internal 5k pullup, now that i have removed the chip i see that someone else on the 'team' pulled off from the layout the external pullup R i had added in case i did not want the reset chip
sigh ...
but then i saw that the line was a nice solid high level, looked at my code and found i had enabled ALL internal pullups for the PIC16F1828 for this project
so the question here is this
as the 'weak' pullup is rather weak (100k ??) do you think i should tack on a lower value one ?
the overall system is large and is too soon to really say that it is working well although at the moment it seems fine as it (I do also have Brown out enabled)
3] if i had wanted to use the reset chip, what might i have done ?
this hi voltage VPP is a nuisance compared to other manufacturers (atmel, silabs), but i am not anxious to to go low voltage programming either as that seems to be a different basket of issues
i have sketched something with some resistors, clamp and steering diodes but it is quite a bit of clutter and parts, putting a jumper on the reset chip would be a royal pain,
just wondering what others have done here ?
(this is different project from the other one i have been chattering about)
when i fired up the hardware i could not program the chip ("target device does not match"),
I 'scoped VPP and saw it was getting clipped, pulled the reset chip and then it programmed fine
so three related questions:
1] i inherited a 0.1uF cap on the MCLR line and i left it in, are the any worries about it slowing down VPP as i notice VPP is pulsing during programming, it seems to work ok, just looking for input from others on this (using MEL U2 programmer)
2] the reset chip is open drain with an internal 5k pullup, now that i have removed the chip i see that someone else on the 'team' pulled off from the layout the external pullup R i had added in case i did not want the reset chip
sigh ...
but then i saw that the line was a nice solid high level, looked at my code and found i had enabled ALL internal pullups for the PIC16F1828 for this project
so the question here is this
as the 'weak' pullup is rather weak (100k ??) do you think i should tack on a lower value one ?
the overall system is large and is too soon to really say that it is working well although at the moment it seems fine as it (I do also have Brown out enabled)
3] if i had wanted to use the reset chip, what might i have done ?
this hi voltage VPP is a nuisance compared to other manufacturers (atmel, silabs), but i am not anxious to to go low voltage programming either as that seems to be a different basket of issues
i have sketched something with some resistors, clamp and steering diodes but it is quite a bit of clutter and parts, putting a jumper on the reset chip would be a royal pain,
just wondering what others have done here ?