From: sergio <smplx@allotrope.net>
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Date: Wed, 17 Feb 2021 13:00:18 -0800
Subject: Re: [EE]:: Simple Task Scheduler written in C
Thread-Topic: [EE]:: Simple Task Scheduler written in C
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oops! hit the wrong key :-)

here's the code:

 	.data

alt_task_pc:	.dsw	1
tmp_bl:		.dsw	1

yield	.macro	arg

 	movf	arg+0,w
 	movwf	tmp_bl+0
 	movf	arg+1,w
 	movwf	tmp_bl+1

; <<<< 	this is the really really important trick!!!
;	use the assembler to generate the return address
;	not an instruction such as "call"

 	movlw	($+8) & 0xff		; low (addr of "lab9")
 	movwf	arg+0
 	movlw	(($+8) >> 8) & 0xff	; high (addr of "lab9")
 	movwf	arg+1

 	movf	tmp_bl+1,w
 	movwf	PCLATH
 	movf	tmp_bl+0,w
 	movwf	PCL

; lab9

 	.endm


new_task .macro	arg1, arg2

 	movlw	(arg2) & 0xff		; low (addr of "task")
 	movwf	arg1+0
 	movlw	((arg2) >> 8) & 0xff	; high (addr of "task")
 	movwf	arg1+1

 	.endm

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

; example of use

 	.code

main:
 	new_task alt_task_pc, task2

lab1_1:

 	; do task1 stuff

 	yield	alt_task_pc

 	; do more task2 stuff

 	yield	alt_task_pc

 	goto lab1

;=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

task2:

lab2_1
 	; do task2 stuff

 	yield	alt_task_pc

 	; do more task2 stuff

 	yield	alt_task_pc

 	goto lab2_1


--=20
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