Siemens C500 User Manual page 35

ACALL addr11
Function: Absolute call
Description: ACALL unconditionally calls a subroutine located at the indicated address. The
instruction increments the PC twice to obtain the address of the following
instruction, then pushes the 16-bit result onto the stack (low-order byte first) and
increments the stack pointer twice. The destination address is obtained by
successively concatenating the five high-order bits of the incremented PC, op code
bits 7-5, and the second byte of the instruction. The subroutine called must
therefore start within the same 2K block of program memory as the first byte of the
instruction following ACALL. No flags are affected.
Example: Initially SP equals 07 H . The label ÓSUBRTNÓ is at program memory location 0345 H .
After executing the instruction
ACALL
at location 0123 H , SP will contain 09 H , internal RAM location 08 H and 09 H will
contain 25 H and 01 H , respectively, and the PC will contain 0345 H .
Operation: ACALL
(PC) ¬ (PC) + 2
(SP) ¬ (SP) + 1
((SP)) ¬ (PC7-0)
(SP) ¬ (SP) + 1
((SP)) ¬ (PC15-8)
(PC10-0) ¬ page address
Encoding: a10 a9 a8 1
Bytes: 2
Cycles: 2
Semiconductor Group
SUBRTN
0 0 0 1 a7 a6 a5 a4 a3 a2 a1 a0
4-9
Instruction Set
C500 Family
1998-04-01