Datasheet

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4.6.4.3 CALLA
CALLA Call a subroutine
CALLA dst
Syntax
Operation dst → tmp 20-bit dst is evaluated and stored
SP – 2 → SP
PC.19:16 → @SP updated PC with return address to TOS (MSBs)
SP – 2 → SP
PC.15:0 → @SP updated PC to TOS (LSBs)
tmp → PC saved 20-bit dst to PC
Description A subroutine call is made to a 20-bit address anywhere in the full address space. All
seven source addressing modes can be used. The call instruction is an address-word
instruction. If the destination address is contained in a memory location X, it is
contained in two ascending words, X (LSBs) and (X + 2) (MSBs). Two words on the
stack are needed for the return address. The return is made with the instruction RETA.
Status Bits N: Not affected
Z: Not affected
C: Not affected
V: Not affected
Mode Bits OSCOFF, CPUOFF, and GIE are not affected.
Examples Examples for all addressing modes are given.
Immediate mode: Call a subroutine at label EXEC or call directly an address.
CALLA #EXEC ; Start address EXEC
CALLA #01AA04h ; Start address 01AA04h
Symbolic mode: Call a subroutine at the 20-bit address contained in addresses EXEC
(LSBs) and EXEC+2 (MSBs). EXEC is located at the address (PC + X) where X is
within +32 K. Indirect addressing.
CALLA EXEC ; Start address at @EXEC. z16(PC)
Absolute mode: Call a subroutine at the 20-bit address contained in absolute addresses
EXEC (LSBs) and EXEC+2 (MSBs). Indirect addressing.
CALLA &EXEC ; Start address at @EXEC
Register mode: Call a subroutine at the 20-bit address contained in register R5. Indirect
R5.
CALLA R5 ; Start address at @R5
Indirect mode: Call a subroutine at the 20-bit address contained in the word pointed to
by register R5 (LSBs). The MSBs have the address (R5 + 2). Indirect, indirect R5.
CALLA @R5 ; Start address at @R5
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SLAU144J–December 2004–Revised July 2013 CPUX
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