Atmel C51 Manual descarregar pdf (Página 63)

The 8051 Instruction Set

1-61 Atmel 8051 Microcontrollers Hardware Manual

4316E–8051–01/07

1.14.50 XCHD A,@R

Bytes: 2

Cycles: 1

Encoding: 1 1 0 0 0 1 0 1 direct address

Operation: XCH

(A) D (direct)

XCH A,@R

Bytes: 1

Cycles: 1

Encoding: 1 1 0 0 0 1 1 i

Operation: XCH

(A) D ((R

))

Function: Exchange Digit

Description: XCHD exchanges the low-order nibble of the Accumulator (bits 3 through 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 following instruction,

XCHD A,@R0

leaves RAM location 20H holding the value 76H (01110110B) and 35H (00110101B) in the Accumulator.

Bytes: 1

Cycles: 1

Encoding: 1 1 0 1 0 1 1 i

Operation: XCHD

3-0

) D ((R

i3-0

))

1 2 ... 58 59 60 61 62 63 64 65 66 67 68 ... 115 116

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Atmel C51 Manual Página 63