Instruction type XRA R in 8085 Microprocessor

Microprocessor8085

In 8085 Instruction, XRA is a mnemonic that stands for “eXclusive OR Accumulator” and “R” stands for any of the following registers, or memory location M pointed by HL pair.

R = A, B, C, D, E, H, L, or M

This instruction is used to Ex-OR contents of R with the Accumulator. The result of Ex-OR operation will be stored in the Accumulator. As R can have any of the eight values, there are eight opcodes for this type of instruction. It occupies only 1-Byte in memory.

Mnemonics, Operand Opcode(in HEX) Bytes
XRA A AF 1
XRA B A8 1
XRA C A9 1
XRA D AA 1
XRA E AB 1
XRA H AC 1
XRA L AD 1
XRA M AE 1

Let us consider XRA E as a sample instruction of this category. It is a 1-Byte instruction so during execution it will occupy only a single Byte in the memory. Let us consider that Accumulator and E registers are having initial contents as ABH and CDH respectively. The result of execution of this instruction has been shown in the following tracing table.

Before After

(E)

CDH CDH

(A)

ABH 66H

(F)

Any values Cy=0,AC=0,S=0,P=1,Z=0

The internal calculation has been done as shown below −

(A) ABH ---> 1010 1011
(E) CDH ---> 1100 1101
             ---------
         XRAE --->0110 0110 (66H)

Address Hex Codes Mnemonic Comment
2004 AB XRA E A = A XOR E

The timing diagram against this instruction XRA E execution is as follows −

XRA E

Summary − So this instruction XRA E requires 1-Byte, 1-Machine Cycle (Opcode Fetch) and 4 T-States for execution as shown in the timing diagram.

raja
Published on 04-Dec-2018 12:12:44
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