instruction time?

[rikotech8]

What is the formula calculating the time needed for one instruction?

[Mike Walne]

I'm assuming you mean assembler instructions not 'C'.

By and large, instructions take one instuction cycle, except jumps which take two. One instruction cycle being four oscillator clock cycles.

Mike

[temtronic]

ie: if using a 4MHz xtal each instruction will take 1usec, except jumps as Mike noted.
if you refer to the datasheet for your PIC there's an entire section that details the 'instruction set'.
hth
jay

[ckielstra]

The MPLAB IDE has a Stopwatch function which I often use when I want to time a sequence of instructions. This also works in the Simulator, so no actual hardware is needed.