Intermec 6200 Reference Guide

R

The following set of interrupts are used for multiĆtasking (AX = 0100h through

0110h):

INT 15h, Function AX = 0100h:  Create a Task

Creates a task and inserts the new task into the ready list.
On Entry:

AH = 01h

AL = 00h

ES:BX = Context pointer

On Return:

CX = New task identifier

The context pointer (ES:BX) points at a structure that looks like the following

Code Fragment:

context struc

dival

dw   ?   ;di register contents for new task

sival

dw   ?   ;si register contents for new task

bpval

dw   ?   ;bp register contents for new task
dw   ?   ;does not care

bxval

dw   ?   ;bx register contents for new task

dxval

dw   ?   ;dx register contents for new task

cxval

dw   ?   ;cx register contents for new task
dw   ?   ;does not care

esval

dw   ?   ;es register contents for new task

dsval

dw   ?   ;ds register contents for new task

ipval

dw   ?   ;ip register contents for new task

csval

dw   ?   ;cs register contents for new task
dw   ?   ;does not care

context ends

csval:ipval specifies the code segment and instruction pointer where the child

task begins execution; the parent task MUST provide them.  The child task

always inherits the flags register from the parent.
Create returns a task ID that is computed with the following equation (ES:BX is

the value passed to the create task function):

Task_id = ((es << 4) + bx) >> 4;

When a newly created task is activated, SS (stack segment) is set to the passed

value of ES (extra segment); SP (stack pointer) is set to the passed value of BX.

The task context is then popped off the stack into the processor registers and an

IRET is executed to pass control to the task.  Thus, the new tasks SS:SP point at

the base" of the context passed during the create command.

INT 15h, Function AX = 0101h:  Delete a Task

On Entry:

AH = 01h

AL = 01h

CX = Task identifier (0 means delete current task)

On Return:

CX = Task identifier (0 if task not found)

ES:BX = Released TCB address