Issue with Array causing PauseUS to have 16uS overhead

I have the following at the top of my code to initialise a 65 byte array to 0:
<code>
for x = 0 to 64
ch[x] = 0
next
</code>

This initialises my array to all 0 values. Problem is that any PauseUS I use after this have an overhead of 16uS, so a PauseUs 8 becomes 24uS.

If I comment out the For...Next loop then the time penalty goes, although I get crap in the array. I assume I must be crossing a code boundary or some such thing and this causes the extra overhead when bank switching occurs.

Any one have any idea ?? I don't really need my PauseUS to be accurate for this, but I am interested how a simple change could cause so much of a latency in another statement.

Any tips on optimisation ??

Using PBP2.47

Thanks,
Bill.

Hi, Bill

Just a stupid basic line :

GOSUB Manual_pauseus_minimum_delay_section '...

Bet your osc is default 4Mhz ...

The only tip :

Insert

@ NOP
.
.
.
.
@ NOP

Alain

The PAUSEUS statement has a minimum time it can delay.
It has to calculate what to do each use at Run-Time.

@ &nbsp;4Mhz, the delay is 24us

A "1us minimum" delay routine can be found here ...
http://www.picbasic.co.uk/forum/showthread.php?p=22098

Another possibility is corruption of the Pause command from using a Bootloader without ...
DEFINE LOADER_USED 1
( but, nobody ever admits to that one. :) )
<br>

The PIC is running at 20MHz. I have Define OSC 20 at the top of the code.
I am not using Interrupts. Its a simple State Machine loop that runs correctly without the For-Next loop that clears the array.

Without the For-Next loop the PauseUS has the correct time, but with it the PauseUS time is way off.

I tried using NOPs, but was still getting a long delay. I think it must an interaction between the for-next loop that clears the array and the HSEROUT.

I borrowed a DSO from work so I can do a bit of in depth investigation into what is happening and why.

I will post the code later when I have it to hand.

bill.

I think CLEAR will zero all your variables without you needing the For..Next lines you now have.

HTH
Brian

Hi, Bill

1) why not try to place your delay comp. just BEFORE the loop ??? ( could help for debugging too ... )

2) you can assign your variables banking ... see $ 7.3



Now, 16µS @ 20 MHz is ~ 60-80 assembler lines ... that make a lot of bank switchings ... if it is bank switching.

What's your processor ???

Alain