
SAM88RCRI INSTRUCTION SET
S3C94A5/F94A5
6-14
CALL
— Call Procedure
CALL
dst
Operation:
SP
@SP
SP
@SP
PC
¨
¨
¨
¨
¨
SP – 1
PCL
SP –1
PCH
dst
The current contents of the program counter are pushed onto the top of the stack. The program
counter value used is the address of the first instruction following the CALL instruction. The specified
destination address is then loaded into the program counter and points to the first instruction of a
procedure. At the end of the procedure the return instruction (RET) can be used to return to the
original program flow. RET pops the top of the stack back into the program counter.
Flags:
No flags are affected.
Format:
Bytes
Cycles
Opcode
(Hex)
Addr Mode
dst
opc
dst
3
14
F6
DA
opc
dst
2
12
F4
IRR
Examples:
Given: R0 = 15H, R1 = 21H, PC = 1A47H, and SP = 0B2H:
CALL
CALL
1521H
@RR0
→
→
SP = 0B0H
(Memory locations 00H = 1AH, 01H = 4AH, where 4AH
is the address that follows the instruction.)
SP = 0B0H (00H = 1AH, 01H = 49H)
In the first example, if the program counter value is 1A47H and the stack pointer contains the value
0B2H, the statement "CALL 1521H" pushes the current PC value onto the top of the stack. The
stack pointer now points to memory location 00H. The PC is then loaded with the value 1521H, the
address of the first instruction in the program sequence to be executed.
If the contents of the program counter and stack pointer are the same as in the first example, the
statement "CALL @RR0" produces the same result except that the 49H is stored in stack location
01H (because the two-byte instruction format was used). The PC is then loaded with the value
1521H, the address of the first instruction in the program sequence to be executed.