# PIC16F877A with a 20MHz oscillator

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#### josh1245

##### Newbie level 5
Helloo!

Can you please tell me how long does a PIC16F877A micro controller take to execute one line of coding when used with a 20 MHz oscillator??

#### Tahmid

fosc = 20MHz
tosc = 1/fosc
tcy = 4 * tosc = 4/fosc

So, tcy = [4/(20 * ${ 10}^{ 6}$)] s = [4/(20 * ${ 10}^{ 6}$)] * ${10 }^{6 }$ µs = 0.2µs = 200ns

Hope this helps.
Tahmid.

#### betwixt

##### Super Moderator
Staff member
Note: Tahmid's figures are for one machine instruction (a single non-branching assember instruction).

One line of code may be considerably longer if it is written in a high level language.

Brian.

#### Tahmid

Yea, the time calculated is that for one instruction cycle.

In assembly, there are a few 2 instruction-cycle instructions.

In high-level language, one line could be 1 instruction cycle or very long, depending on the line of code.

#### josh1245

##### Newbie level 5
thank you soo much Tahmid, & Brain... since Im new to micro controllers, I am using MicroC, but not assembly.., can you please tell me how it works with microC if you do not mind.??

#### Tahmid

It depends on the instruction / line of code. You can use the stopwatch option in the debugger to check the time.

#### Ishah

##### Member level 1
It depends on the instruction / line of code. You can use the stopwatch option in the debugger to check the time.

Hi Tahmid,

Can you guide me to fill this stop watch of MicroC.

#### FvM

##### Super Moderator
Staff member
Stopwatch runs between breakpoints or single steps in debugging. Nothing to fill out.

#### Ishah

##### Member level 1
Stopwatch runs between breakpoints or single steps in debugging. Nothing to fill out.
Sorry Im new of this, it's quiet shame for me to ask but, it that mean I need to click F9 (start Debugger) ? Where i can check the time.. ?

Thanks FvM.

#### FvM

##### Super Moderator
Staff member
that mean I need to click F9 (start Debugger) ?
I'm sure you'll also find out which hotkeys are available to access
- breakpoints
- single stepping

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