LOAD value in HELP

hgrueneis · Joined: 04 Apr 2009 Posts: 902 Location: A-4786 Brunnenthal

The Load value in Help is not supposed to be calculated from 256 but 255 for 8-bit Timers.
"Load Timer0, 10", will load the timer with a value of 245.
Respectively for 16-bit, not from 65536 but 65535.
Count position and count value differ by 1.
Not a big deal but it can have a big effect.
Best regards
Hubert

Quote of text in LOAD HELP:

The TIMER0 does not have a reload mode. But when you want the timer to generate an interrupt after 10 ticks for example, you can use the LOAD statement.

It will do the calculation : (256-value)

So LOAD TIMER0, 10 will load the TIMER0 with a value of 246 so that it will overflow after 10 ticks.

TIMER1 is a 16 bit counter so it will be loaded with the value of 65536-value.

albertsm · Joined: 09 Apr 2004 Posts: 5922 Location: Holland

i do not understand what you mean.
from the help and my understanding of timers :

hgrueneis · Joined: 04 Apr 2009 Posts: 902 Location: A-4786 Brunnenthal

Yes, I know.
Maybe I did not express myself the right way.
The fact is, that there is no value of 256 in an 8-bit system,
other than an overflow that would again represent 0.
The overflow occurs to 0 from 255 Value (the 256th counter state with value 255).
There is no 256 which would be H100 or B1_0000_0000 and therefore 9-bit,
overflow without an additional complete clock cycle to go to 0.
After value 255 it goes directly to B0000_0000.
At least that is my view of the matter.
Best regards
Hubert

albertsm · Joined: 09 Apr 2004 Posts: 5922 Location: Holland

yes i know all that Very Happy

but this is what i wrote ;
it will do the calculation : (256-value)

So LOAD TIMER0, 10 will load the TIMER0 with a value of 246 so that it will overflow after 10 ticks.

To make it simpler here is a value for 1 : 256-1=255.
So when i want the timer to overflow after one tick, i need to load 255. with one clock , the timer overflows to 0 causing the interrupt flag to be set.
I hope it is clear now.