Intel 80286, 80287 manual Flags Modified, Flags Undefined, Operation, Call

THE 80286 INSTRUCTION SET

CALL-Call Procedure

Opcode		Instruction		Clocks'	Description
E8	cw	CALL	cw	7	Call near, offset relative to next instruction
FF	/2	CALL	ew	7,mem=11	Call near, offset absolute at EA word
9A	cd	CALL	cd	13,pm=26	Call inter-segment, immediate 4-byte address
9A	cd	CALL	cd	41	Call gate, same privilege
9A	cd	CALL	cd	82	Call gate, more privilege, no parameters
9A	cd	CALL	cd	86+4X	Call gate, more privilege, X parameters
9A	cd	CALL cd		177	Call via Task State Segment·
9A	cd	CALL	cd	182	Call via task gate
FF	/3	CALL	ed	16,mem=29	Call inter-segment, address at EA doubleword
FF	/3	CALL	ed	44	Call gate, same privilege
FF	/3	CALL	ed	83	Call gate, more privilege, no parameters
FF	/3	CALL	ed	90+4X	Call gate, more privilege, X parameters
FF	/3	CALL	ed	180	Call via Task State Segment
FF	/3	CALL	ed	185	Call via task gate

·Addone clock for each byte in the next instruction executed.

FLAGS MODIFIED

None, except when a task switch occurs

FLAGS UNDEFINED

None

OPERATION

The CALL instruction causes the procedure named in the operand to be executed. When the procedure is complete (a return instruction is executed within the procedure), execution continues at the instruc- tion that follows the CALL instruction.

The CALL cw form of the instruction adds modulo 65536 (the 2-byte operand) to the offset of the instruction following the CALL and sets IP to the resulting offset. The 2-byte offset of the instruction that follows the CALL is pushed onto the stack. It will be popped by a near RET instruction within the procedure. The CS register is not changed by this form.

The CALL ew form of the instruction is the same as CALL cw except· that the operand specifies a memory location from which the absolute 2-byte offset for the procedure is fetched.

The CALL cd form of the instruction uses the 4-byte operand as a pointer to the procedure called. The CALL ed form fetches the long pointer from the memory location specified. Both long pointer forms consult the AR byte in the descriptor indexed by the selector part of the long pointer. The AR byte can indicate one of the following descriptor types:

l.Code Segment-The access rights are checked, the return pointer is pushed onto the stack, and the procedure is jumped to.

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