STC89C53RC datasheet(76/165 Pages) STC

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XCH A, @Ri

Bytes:

Cycles:

Encoding:

1 1 0 0

0 1 1 i

Operation:

XCH

(A)

((Ri))

XCHD

A, @Ri

Function:

Exchange Digit

Description:

XCHD exchanges the low-order nibble of the Accumulator (bits 3-0), generally representing

a hexadecimal or BCD digit, with that of the internal RAM location indirectly addressed by

the specified register. The high-order nibbles (bits 7-4) of each register are not affected. No

flags are affected.

Example:

R0 contains the address 20H. The Accumulator holds the value 36H (00110110B). Internal

RAM location 20H holds the value 75H (01110101B). The instruction,

XCHD

A, @R0

will leave RAM location 20H holding the value 76H (01110110B) and 35H (00110101B) in

the accumulator.

Bytes:

Cycles:

Encoding:

1 1 0 1

0 1 1 i

Operation:

XCHD

(A3-0)

(Ri3-0)

XRL

<dest-byte>, <src-byte>

Function:

Logical Exclusive-OR for byte variables

Description:

XRL performs the bitwise logical Exclusive-OR operation between the indicated variables,

storing the results in the destination. No flags are affected.

The two operands allow six addressing mode combinations.When the destination is the

Accumulator, the source can use register, direct, register-indirect, or immediate addressing;

when the destination is a direct address,the source can be the Accumulator or immediate data.

(Note: When this instruction is used to modify an output port, the value used as the original

port data will be read from the output data latch, not the input pins.)

Example:

If the Accumulator holds 0C3H (11000011B) and register 0 holds 0AAH (10101010B) then

the instruction,

XRL

A, R0

will leave the Accumulator holding the vatue 69H (01101001B).

When the destination is a directly addressed byte, this instruction can complement combinna-

tion of bits in any RAM location or hardware register. The pattern of bits to be complemented

is then determined by a mask byte, either a constant contained in the instruction or a variable

computed in the Accumulator at run-time. The instruction,

XRL

P1, #00110001B

will complement bits 5,4 and 0 of outpue Port 1.

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