On Mar 31, 2:09 pm, "m...@watty" <[email protected]> wrote: > According to ALL the Microchip ICSP schematics: > 1) VPP connects direct to MLCR pin. no resistors or diodes. > > 2) VPP/MCLR is connected to rest of circuits (reset buttons, VDD, R &C > reset time constant, what ever you want) via a diode (to block VPP > > VDD) OR a resistor (to limit VPP to VDD current) AND ALSO the resistor > OR diode means the capacitor is NOT directly connected to MCLR/VPP, to > avoid damp rise time of VPP too much. > > Basic principle. > > 1) Vpp pin connects DIRECT to MCLR pin > > 2) have what you like for reset circuit, but either a diode or > resistor or something to limit OR block VPP -> VDD current flow and > ensure rise time of VPP is not compromised. > > so on your schematic dump the series diode on VPP. > disconnect MCLR from everything and connect it direct to VPP and other > end of the 1K ohm resistor. > Then the circuit meets Microchip specs. > > See help file of pickit 2 in MPLAB readmes, or Pickit 2 or 3 user > manual under ICSP.
use the diode you took out of vpp -> 1k -> Mclr to go from c4 to Vdd/ 5V as a clamp. Otherwise when serial port goes --|_|--- the rising pulse can be enough to put PIC into programming mode. I've seen program corruption with Vpp spikes on MCLR if the data & clock pinds RB6/RB7 happen to change too. -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
