MDOS Multitasking

[+9640News]

Tim,

 

I used to have the information from Paul Charlton, but can not find it anymore. Looking at my Windows source, I do not believe I had the information there as well.

 

I have a program that is calling up another program with the Utility XOP. Program loads and executes, however, I do not recall the byte(s) I need to have the calling program write to >0102 to put the parent program to sleep with the byte(s) at >0102 of the child task to make it exclusive. I know the CLI is a unique task and it was different, but did not recall the bytes needed to write and I can not find my notes on the subject.

 

I seem to recall needing to stay in a loop waiting for the time slice to decrement to 0, but nothing I have tried thus far works.

 

The closest I have gotten thus far to anything that works is writing >FF01 to >0102 of the parent program and >FE06 to the child task at >0102. However, when I exit the child task, the parent does not re-awaken.

 

Beery

 

 

 

[+9640News]

Low and behold, I found my notes on the subject and someone had posted them on the internet;

 

The link is: http://ti994a.cwfk.net/9640news/volume1-5.html

 

The notes I needed are:

 

Notes on >0102 as the 'task' state used by the interrupt routine to determine the status of each task

if the state is >00, the task is in run mode and can be swapped to another task by the interrupt routine.

if the state is >FF (reserved for the CLI), the interrupt routine ignores the task if there are other tasks present.

if the task is >FE, the task is locked and can not be multi-tasked

if the task is >FD, the task is ignored and prgrams like the CLI in state >FF can still run (used to lock a tasks memory pages so they can't be freed, like the graphics drivers, or other code for a library)

if the state is >01...>fc, the task is assumed to be asleep, waiting for the I/O or something and the interrupt routine ignores the CLI

What Paul says about >0102 is it is a counter that is decremented by the interrupt routine that runs every 1/60 second. When it reaches >0000, another task is mapped in and runs until it is is decremented. The interrupt routine first determines the state of those tasks. That is why I mapped >0000 into the CLI to make it an even run time task. When I move >0001 into my task (can't go smaller), it is decremented to zero and only stays in the task about 1/16 the time it would have normally been there. Note this is only good for v0.96H (I haven't checked V1.14F to see if those bytes are in the same location. If you use DISkASSEMBLER and disassemble pages >06 and find where it moves bytes into location >0102, you can check for other versions if those bytes assembled out of position.

[+9640News]

Just a snippit of code for anyone should they ever want to do something similar.

 

LI R0,>27

LI R1,STRING

LI R2,10

XOP @VID,0

LI R0,9

LI R1,STR

XOP @UTIL,0

LIMI 0

MOV R1,@>F112

MOV @HEXFE06,@>6102

MOV @HEXFF01,@>0102

MOV @HEX0602,@>F112 Mapping the CLI in.

MOV @HEXFC01,@>4102 Changing the state of the CLI

LIMI 2

REDO

LI R0,>27

LI R1,STRING1

LI R2,10

XOP @VID,0

LI R0,>27

LI R1,STRING2

LI R2,10

XOP @VID,0

JMP REDO

BLWP @0

STRING TEXT 'Hello '

BYTE >0D,>0A,0

EVEN

VID DATA 6

UTIL DATA 9

HEXFE DATA >FEFE

HEX0003 DATA >0003

HEXFD00 DATA >FB00

HEXFDFF DATA >FDFF

HEXFE06 DATA >FE06

HEXFF01 DATA >FF01

HEX0602 DATA >0602

HEXFC01 DATA >FC01

STR BYTE 18

TEXT 'HDS1.MDOS1.PROGRAM"

EVEN

STRING1 TEXT 'GO UK '

BYTE >0D,>0A,0

EVEN

STRING2 TEXT 'HEY '

BYTE >0D,>0A,0

EVEN

Edited February 28, 2018 by BeeryMiller

[+9640News]

i had to add 4 lines of code to the above code. I needed to change the state of the CLI so it would not preempt the parent program after its state had changed. This means, once you have exited the child program and the parent program takes over, you need to allow enough time to then change the state of the CLI back to its original state. This can be done on a timer loop, or during a clean exit of the calling program.

 

Beery