STC89C53RC datasheet(59/165 Pages) STC

59 / 165 page

rel

Function:

Jump if Accumulator Zero

Description:

If all bits of the Accumulator are zero, branch to the address indicated; otherwise proceed

with the next instruction. The branch destination is computed by adding the signed relative-

displacement in the second instruction byte to the PC, after incrementing the PC twice. The

Accumulator is not modified. No flags are affected.

Example:

The Accumulator originally contains 01H. The instruction sequence,

LABEL1

DEC

LAEEL2

will change the Accumulator to 00H and cause program execution to continue at the

instruction identified by the label LABEL2.

Bytes:

Cycles:

Encoding:

0 1 1 0

0 0 0 0

rel. address

Operation:

(PC) ← (PC)+ 2

← (PC)+ 2

(PC)+ 2

IF (A) = 0

THEN

(PC) ← (PC) + rel

← (PC) + rel

(PC) + rel

LCALL addr16

Function:

Long call

Description:

LCALL calls a subroutine loated at the indicated address. The instruction adds three to the

program counter to generate the address of the next instruction and then pushes the 16-bit

result onto the stack (low byte first), incrementing the Stack Pointer by two. The high-order

and low-order bytes of the PC are then loaded, respectively, with the second and third bytes

of the LCALL instruction. Program execution continues with the instruction at this address.

The subroutine may therefore begin anywhere in the full 64K-byte program memory address

space. No flags are affected.

Example:

Initially the Stack Pointer equals 07H. The label “SUBRTN” is assigned to program memory

location 1234H. After executing the instruction,

LCALL SUBRTN

at location 0123H, the Stack Pointer will contain 09H, internal RAM locations 08H and 09H

will contain 26H and 01H, and the PC will contain 1234H.

Bytes:

Cycles:

Encoding:

0 0 0 1

0 0 1 0

addr15-addr8

addr7-addr0

Operation:

LCALL

(PC) ← (PC) + 3

← (PC) + 3

(PC) + 3

(SP) ← (SP)+1

← (SP)+1

(SP) + 1

((SP)) ← (PC

← (PC

(PC

7-0)

(SP) ← (SP)+1

← (SP)+1

(SP) + 1

((SP)) ← (PC

← (PC

(PC

15-8)

(PC) ← addr

← addr

addr

15-0

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