issue with DEBUG, please help

[Lazuli]

Doing some test, I realized that it is the instruction:
OPTION_REG = OPTION_REG & $80 | 1 ; Set TMR0 Prescaler to 256, leave RBPU alone

which makes the DEBUG to produce garbage, as if the baud rate was wrong. This line was taken from the example of Darrel for the clock. So it seems it affects the DEBUG instruction.
Could someone explain me the root cause and how to overcome this issue.
This is my first attempt at using timer and interrupt and I am really in unknown territory here. I will keep doing some reading but any help will be highly appreciated.
thanks,
Olivier

[HenrikOlsson]

Hi,

If an interrupt occurs while the DEBUG statement is busy outputting data it will, as the mechanism name implies, be interrupted and since it's a bitbanged software timed routine its timing will be off which in turn means garbage data.

Either use the USART ("manually" or with HSEROUT) to send the data or make sure to turn off or mask the interrupts WHILE the DEBUG statement is executing.

/Henrik.

[richard]

OPTION_REG = OPTION_REG & $80 | 1 ; Set TMR0 Prescaler to 256, leave RBPU alone

por value for OPTION_REG is 255 (0b11111111)

OPTION_REG & $80 | 1 results in OPTION_REG =129 (0b10000001)
that is not the result you are describing in your comment ; Set TMR0 Prescaler to 256, leave RBPU alone
it also sets the int Interrupt to falling edge of INT pin
for 256 prescaler OPTION_REG bits 0:2 = 0b111

next issue your code is not posted in code tags which makes life difficult .

what do you think will happen to the bit timing accuracy of a software timed serial output routine like debug when you interrupt it 100's of times per second

[Lazuli]

Thank you for the explanation, it is clear now. I just need to modify my board now to use the USART instead

And for next time in order to post code properly, what do you call code tags? Is it the "wrap QUOTE tags" option in the editor?

thanks,
Olivier

[andywpg]

And for next time in order to post code properly, what do you call code tags? Is it the "wrap QUOTE tags" option in the editor?

Nope.  You have to go the advanced editor (at least I do) and select 'Wrap CODE tags'.  Looks like this:  #
Creates a window like this that you can scroll up and down in