|
| |
Call Procedure
|
86/88 |
Y |
186 |
Y |
286 |
Y |
386 |
Y |
486 |
Y |
CALL procedure |
|
Ovfl |
N |
Dir |
N |
Int |
N |
Trap |
N |
Sign |
N |
Zero |
N |
Aux |
N |
Prty |
N |
Carry |
N |
CALL transfers control to a procedure that can either be within the
current segment (a NEAR procedure) or outside it (a FAR procedure).
The two types of CALLs result in different machine instructions, and
the RET instruction that exits from the procedure must match the type
of the CALL instruction (the potential for mismatch exists if the
procedure and the CALL are assembled separately).
Notes: For an inter-segment procedure (procedure in a
different segment), the processor first pushes the
current value of CS onto the stack, then pushes the
current value of IP (which is pointing to the
instruction following the CALL instruction), then
transfers control to the procedure.
For an intra-segment procedure (procedure in the
same segment), the processor first pushes the
current value of IP (which is pointing to the
instruction following the CALL instruction) onto the
stack, then transfers control to the procedure.
CALL can also read the procedure address from a
register or memory location. This form of CALL is
called an indirect CALL.
------------------------------------ Timing ----------------------------------
OpCode Instruction 386 286 86
E8 cw CALL rel16 7+m 7 19
FF/2 CALL r/m16 7/10+m 7/11 16/21+EA
9A cd CALL ptr16:16 17+m 13 28
call gate, same priveledge 52+m 41
call gate, more priv, no params 86+m 82
call gate, more priv, X params 94+4X 86+4X
call to task ts 177/182
FF/3 CALL m16:16 22+m 16/29 37+EA
call gate, same priveledge 56+m 44
call gate, more priv, no params 90+m 83
call gate, more priv, X params 98+4x 90+4x
call to task 5+ts 180/185
E8 cd CALL rel32 7+m
FF/2 CALL r/m32 7/10+m
9A cp CALL ptr16:32 17+m
call gate, same priveledge 52+m
call gate, more priv, no params 86+m
call gate, more priv, X params 94+4x+m
call to task ts
FF/3 CALL m16:32 22+m
call gate, same priveledge 56+m
call gate, more priv, no params 90+m
call gate, more priv, X params 98+m
call to task 5+ts
------------------------------------ Logic -----------------------------------
if FAR CALL (inter-segment)
PUSH CS
CS = dest seg
PUSH IP
IP = dest ofs
See Also RET JMP INT |