Does variable value change being transferred to code running in interrupt loop?

[Dave]

CuriousOne, Here ia a small template for a program I just wrote that you can use as a starting point. It uses DT interrupts. I have them set for 1 millisecond and using 2 complete ports for the leds. Those ports are B & D. These interrupts are running in the background updating the led status from the 16 byte array. You can change the values in the array at any time in the main program. Enjoy. Let me know if it works for you.

[CuriousOne]

Thanks a lot, I don't have 18F46K22, but I have 18F45K22, will give it a try.

I need some time to read and interpret "foreign" code for myself

[CuriousOne]

Here's how I understand, how interrupt should work (for my case of course).

There are two "independent" code blocks. The MCU works like this - 4 clock ticks (if I'm not mistaken, minimal amount needed to execute one command) are given to code block #1, next 4 ticks - to block #2, and so on. Since these "ticks" are going at high speed, from the user side, response is fluid and smooth.

am I wrong?

[Dave]

CuriousOne, It sounds as if you are interpreting interrupts to mean time multiplexing the operations of 2 different code segments at 50 %. This is NOT how it works. The MAIN code seqment is interrupted for a short period of time do execute some code then execution is returned to the main seqment. You should be in the interrupt routine as short of a time as possible.

[CuriousOne]

Yes, I might be wrong, since I approach interrupts as sort of multi-tasking. So, it might be possible to use it in they way I'd like it to be?

Like this sequence:

program starts, timer1 starts counting and after 4 ticks (or whatever value needed) it generates interrupt which jumps to another part of code. That another part of code, itself launches timer2, which again, after 4 ticks or whatever, generates interrupt, which jumps to 1st part of code.

Is this possible?

I guess, ASM will be needed.

[Dave]

Wow, If that's all you want to do is jump between two different programs at a fixed interval then I would just start a timer interrupt at your favorite interval then TOGGLE a BIT called "PROG" each time the interrupt occures as well as set a flag bit called "Interrupt" to indicate the interrupt has occured. Then your main program would look like:
MAIN:
if Interrupt = 1 then
Interrupt = 0
if PROG = 0 then
gosub program 1
else
gosub program 2
endif
endif
goto main

[CuriousOne]

Yes, but program should not be terminated, it should be "paused" while another part is executing. Let me illustrate by this simple "CODE"

Conventional BASIC:

DO:
FOR A=1 TO 10
PRINT "A=";A
NEXT A

FOR B=1 TO 10
PRINT "B=";B
NEXT B

LOOP

The above program will print value of A first, and then it will print value of B.

But I need a output like this:

A=1
B=1
A=2
B=2
A=3
B=3

and so on.

I need to somehow "multiplex" two different parts of code in a such way, that they would run in "parallel" If you have heard about Parallax "propeller" chip, which has 8 "cores" but they being executed sequentally, at high speed, so user gets feeling of multi-core system. So I want basically to emulate something like that.