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Instruction Type LXI rp, d16 in 8085 Microprocessor

In the 8085 Instruction set there are four instructions, which belong to the type LXI rp, d16. These instructions are used to load the 16-bit address into the register pair. We can use this instruction to load data from memory location using the memory address, which is stored in the register pair rp. For an example, if the instruction is LXI H, FE50. It means that the FE50 is loaded into the HL register pair.

The rp can be BC, DE, HL or SP.

The LXI instructions and their Hex-codes are as follows.

Mnemonics, Operand Opcode (in HEX) Bytes
LXI B 01 3
LXI D 11 3
LXI H 21 3
LXI SP 31 3

Example

In this example, we can see how the LXI instruction can load 16-bit data into the Register Pairs.

Load 56FE into the DE register pair and ABCD into the HL register pair, exchange the content of DE and HL. And store the content of DE register pair into the location 8050 and 8051H.

Address Hex Codes Mnemonic Comment
8000

11

FE

56

 LXI D, 56FEH Store 56FEH into the DE Register Pair.
8003

21

CD

AB

 LXI H, ABCDH Store ABCDH into the HL Register Pair.
8006 EB XCHG Exchange the content of DE and HL
8007

21

50

80

 LXI H, 8050H Load 8050H into the HL pair to store the result.
800A 72 MOV M, D Store the content of register D into the memory location.
800B 23 INX H Point HL to next source location
800C 73 MOV M, E Store the content of register E into the memory location.
800D 76 HLT Stop

Output
Address Value
8050H AB
8051H CD

Following is the timing diagram of the instruction LXI D, 56FEH

56FEH

Summary − So this instruction LXI D, 56FEH requires 3-Bytes, 3-Machine Cycles (Opcode Fetch, Memory Read, Memory Read) and 10 T-States for execution as shown in the timing diagram.

Samual Sam
Samual Sam

Learning faster. Every day.

Updated on 30-Jul-2019 22:30:23

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