STC89LE53RC datasheet(57/165 Pages) STC

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JMP

@A+DPTR

Function:

Jump indirect

Description:

Add the eight-bit unsigned contents of the Accumulator with the sixteen-bit data pointer,

and load the resulting sum to the program counter. This will be the address for subsequent

instruction fetches. Sixteen-bit addition is performed (modulo 216): a carry-out from the low-

order eight bits propagates through the higher-order bits. Neither the Accumulator nor the

Data Pointer is altered. No flags are affected.

Example:

An even number from 0 to 6 is in the Accumulator. The following sequence of instructions

will branch to one of four AJMP instructions in a jump table starting at JMP_TBL:

MOV

DPTR, #JMP_TBL

JMP

@A+DPTR

JMP-TBL:

AJMP

LABEL0

AJMP

LABEL1

AJMP

LABEL2

AJMP

LABEL3

If the Accumulator equals 04H when starting this sequence, execution will jump to label

LABEL2. Remember that AJMP is a two-byte instruction, so the jump instructions start at

every other address.

Bytes:

Cycles:

Encoding:

0 1 1 1

0 0 1 1

Operation:

JMP

(PC) ← (A) + (DPTR)

← (A) + (DPTR)

(A) + (DPTR)

JNB bit, rel

Function:

Jump if Bit is not set

Description:

If the indicated bit is a zero, branch to the indicated address; otherwise proceed with the next

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

in the third instruction byte to the PC, after incrementing the PC to the first byte of the next

instruction. The bit tested is not modified. No flags are affected.

Example:

The data present at input port 1 is 11001010B. The Accumulator holds 56H (01010110B).

The instruction sequence,

JNB

P1.3, LABEL1

JNB

ACC.3, LABEL2

will cause program execution to continue at the instruction at label LABEL2

Bytes:

Cycles:

Encoding:

0 0 1 1

0 0 0 0

bit address

rel. address

Operation:

JNB

(PC) ← (PC)+ 3

← (PC)+ 3

(PC)+ 3

IF (bit) = 0

THEN

(PC) ← (PC) + rel

← (PC) + rel

(PC) + rel

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