How can I get Timer 1 to overflow every 5 seconds

[Acetronics2]

...

The only solution for timer 1 to overflow every 5 sec is to run the CPU clock @ 400 khz ...

Depends on what you intend to do ...

but

IF I detect something

Do something .... for 5 sec

Wait for detect.

Generally is solved by sleep/ wake use of the µP ...

Alain

[revelator]

thanks scalerobotics and acetronics...I guess I had answer my own question

"...Can I use Timer0 as another prescaler to Timer1?...

I guess I could use Timer0 and at overflow set any available pin high then low (generate a pulse) and use it as input (via hardwire) to another timer which would be set to read an external clock (that would be the pulse).

Thinking out of the box.....

thanks again

[rmteo]

Just increment/count a variable in the TIMER1 interrupt service routine and you can achieve any interval that you want - from fractions of a second to hours.

[Acetronics2]

...

The only solution for timer 1 to overflow every 5 sec is to run the CPU clock @ 400 khz ...

Alain

Oh, Oh ...

I had forgotten the 876 timer1 simply could be driven by its own oscillator up to 200 Khz ... ( NOT the CPU Osc @ 20 Mhz !)

so, no problem ... 32768 Hz are easy to find Xtals !

note also exist " Gate driven " Timers on numerous chips ( see 12f 683 i.e)

Alain