Electronics > Beginners

CPU Reset

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gkmaia:
This circuit attached is an extract of my Roland RD300s circuit.

My question regards the RESET pin. By looking at the schematics i understand is the reset is HIGH the CPU will be halt. In most CPUs the reset has to go LOW to halt thee CPU. But according to this schematic it is the opposite.

Anyway... by looking at the circuit I see when ON a voltage being applied to the base of Q2, Q2 then conducts bringing the base of Q1 to ground. Q1 the is open holding it's collector and the RES pin at +5v. And by the schematics and IC datasheet if res is HIGH the IC is halt.

What am I getting wrong here?

ataradov:
During steady state Q1 is open, which keeps Q2 closed. So reset is high during normal operation, just like any other MCU.

And I could only google some repair manuals, not the datasheets. If you are judging by not having a line over the RESET name, then I would not trust that. If there is some test that explicitly stated that reset is active high, then where it is?

Also, I found a manual where RES pin is marked as active negative. And the same exact circuit is used.

gkmaia:
Thanks!

That solves the problem pretty much.

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