SLEEP mode 16F628A

[Jerson]

Hi Michael

I'm not sure if this will help. The sleep statement needs to be followed by at least a nop. Read the datasheet carefully - it has a mention of this. Anyway, I am too lazy to read it and point it out at this time. I use the 16F628A in sleep and successfully.

The statement sequence should be

@sleep
@nop
@nop

Also, make sure that the pending interrupt is cleared before you put the PIC to sleep.

Jerson

[Michael]

Ok....that's a new one. A NOP?

Everything I think is fine...as always a stupid mistake on my part by not taking PORTB.0 low with a pulldown and letting it float....(a great way to get "unpredictable" behavior).

It was probably sensing a false high and interfering with the sleep routine.

I had put a pause following sleep as I had read in the archives (Melanie?) suggested it's use, to let the PIC wake up and get some coffee.

Maybe what your saying is the NOP would do the same thing?

Sort of a safety buffer before it gets back to work?

[Jerson]

See section 14.8.1 of the datasheet on page 110/168. This is the excerpt

When the SLEEP instruction is being executed, the
next instruction (PC + 1) is pre-fetched. For the device
to wake-up through an interrupt event, the correspond
ing interrupt enable bit must be set (enabled). Wake-up
is regardless of the state of the GIE bit. If the GIE bit is
clear (disabled), the device continues execution at the
instruction after the SLEEP instruction. If the GIE bit is
set (enabled), the device executes the instruction afte
the SLEEP instruction and then branches to the inter
rupt address (0004h). In cases where the execution of
the instruction following SLEEP is not desirable, the
user should have an NOP after the SLEEP instruction.

Jerson