Resetting a slave from master mcu

[amgen]

crap, I figured you were a kid ..... I always put the pics in sockets, saves a lot of F-ups. For transistor, logic level MOSFET is good to use. The logic level means it will be full on with 5 volts on gate, no resistors required.... N-channel like BS170 ... with this, the reset is a high pulse on master...(dah)

[richard]

I'm doing regular ICSP programming for now

any pic programmer worth its salt can program chips that support LVP in "regular ICSP" mode without that nasty hv pulse being needed at all

[Demon]

any pic programmer worth its salt can program chips that support LVP in "regular ICSP" mode without that nasty hv pulse being needed at all

Low-voltage programming is not used by melabs programmers and should always be disabled in the configuration settings.

https://melabs.com/support/icsp.htm


I'm gonna take my PicKit4 out of storage and give it another shot.

[Demon]

crap, I figured you were a kid .....

I'm a kid at heart, and I get out of bed at the same speed as them.

..... I always put the pics in sockets, saves a lot of F-ups....

Yeah, I'd hate to notice a mistake at the end of assembling my boards.

... For transistor, logic level MOSFET is good to use. The logic level means it will be full on with 5 volts on gate, no resistors required.... N-channel like BS170 ... with this, the reset is a high pulse on master...(dah)

I finally got a few SN7407 thanks to Mr E's suggestion a while back. This runs awesome, and I have room for 6 slaves, that should be enough for my boards.




I don't have to worry about the surges up towards the Master during programming the Slave.

(Which is good, cause my MeLabs U2 programmer doesn't do LVP, and I can't get my PicKit4 to run properly).

[richard]

I don't have to worry about the surges up towards the Master during programming the Slave.

No, but the 120 ohm pullup will be a pin killer if the vdd is 5v

[Demon]

No, but the 120 ohm pullup will be a pin killer if the vdd is 5v

Yeah, I was blindly following SN7407 datasheet. I don't really care about timing, so I upped it to 1K pull-up.

[richard]

Yeah, I was blindly following SN7407 datasheet. I don't really care about timing, so I upped it to 1K pull-up.

given that I-inh max for a SN7407 gate is 40uA and a pic output pin could drive more than 20 of them and still produce a clean TTL signal.
i cannot see that signal timing would even be a consideration. just what need does the pullup fulfill ?

[Demon]

given that I-inh max for a SN7407 gate is 40uA and a pic output pin could drive more than 20 of them and still produce a clean TTL signal.
i cannot see that signal timing would even be a consideration. just what need does the pullup fulfill ?

Except from preventing the input pin on the SN7407 from floating, I don't see one for my application.

I don't really care about "precision timing"; I just trigger the MCLR reset on the Slave with a 10usec pause. I still have a pull-up downstream on the Slave PIC.

SlaveMCLR = 0
PauseUS 10
SlaveMCLR = 1

EDIT: I figured I'd read the instructions AFTER posting that reply.

11.1 Layout Guidelines: ... All unused inputs of digital logic devices must be connected to a high or low bias to prevent them from floating.

Promptly runs over to breadboard to pull down the other 5 unused inputs.