XCALL *AL
6-374
XCALL *AL C2 x LP Source-Compatible Function Call
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
XCALL *AL 0101 0110 0011 0100 1 − 7
Operands *AL Indirect program-memory addressing using register AL, can only access
high 64K of program space range (0x3F0000 to 0x3FFFFF)
Description Indirect call with destination address in AL. The lower 16 bits of the current
PC address are saved onto the software stack. Then, the low 16 bits of PC is
loaded with the contents of register AL and the upper 6 bits of the PC are
loaded with 0x3F:
temp(21:0) = PC + 1;
[SP] = temp(15:0);
SP = SP + 1;
C = 0x3F:AL;
Note: This instruction can only transfer program control to a location located in the upper 64K
range of program space (0x3F0000 to 0x3FFFFF). To return from a call made by
XCALL, the XRETC instruction must be used.
Flags and
Modes
None
Repeat This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
Example
; Call function in FuncTable selected by FuncIndex value.
; This example only works for code located in upper 64K of
; program space:
FuncTable: ; Function address table:
.word FuncA ; FuncA address
.word FuncB ; FuncB address
.
.
MOVL XAR2,#FuncTable ; XAR2 = pointer to FuncTable
MOVZ AR0,@FuncIndex ; AR0 = FuncTable index
MOV AL,*+XAR2[AR0] ; AL = Table[FuncIndex]
XCALL *AL ; Indirect call using AL
.
.
FuncA: ; Function A:
.
.
XRETC UNC ; Return unconditionally
FuncB: ; Function B:
.
.
XRETC UNC ; Return unconditionally
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