INSTRUCTION SET

S3C84E5/C84E9/P84E9

 

 

CALL — Call Procedure

CALL dst

Operation: SP SP–1

@SP PCL

SP SP–1

@SP PCH

PC dst

The 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

Addr Mode

 

 

 

 

 

 

(Hex)

dst

 

 

 

 

 

 

 

 

 

opc

dst

3

14

F6

DA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

opc

dst

 

2

12

F4

IRR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

opc

dst

 

2

14

D4

IA

 

 

 

 

 

 

 

 

Examples:

Given:

R0 = 35H, R1 = 21H, PC = 1A47H, and SP = 0002H:

 

CALL

3521H

SP = 0000H

 

 

 

 

(Memory locations 0000H = 1AH, 0001H = 4AH,

 

 

 

 

where, 4AH is the address that follows the instruction.)

 

CALL

@RR0

SP = 0000H (0000H = 1AH, 0001H = 49H)

 

CALL

#40H

SP = 0000H (0000H = 1AH, 0001H = 49H)

In the first example, if the program counter value is 1A47H and the stack pointer contains the value 0002H, the statement "CALL 3521H" pushes the current PC value onto the top of the stack. The stack pointer now points to the memory location 0000H. The PC is then loaded with the value 3521H, the address of the first instruction in the program sequence to be executed.

If the contents of the program counter and the 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 0001H (because the two-byte instruction format was used). The PC is then loaded with the value 3521H, the address of the first instruction in the program sequence to be executed. Assuming that the contents of the program counter and the stack pointer are the same as in the first example, if the program address 0040H contains 35H and the program address 0041H contains 21H, the statement "CALL #40H" produces the same result as in the second example.

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Samsung S3C84E5 user manual Call Call Procedure, Call dst Operation SP ← SP-1, @Sp ← Pcl, @Sp ← Pch