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Instruction type LDA a16 in 8085 Microprocessor
In 8085 Instruction set, LDA is a mnemonic that stands for LoaD Accumulator with the contents from memory. In this instructionAccumulatorwill get initialized with 8-bit content from the 16-bit memory address as indicated in the instruction as a16. This instruction uses absolute addressing for specifying the data. It occupies 3-Bytes in the memory. First Byte specifies the opcode, and the successive 2-Bytes provide the 16-bit address, i.e. 1-Byte each for each memory location.
| Mnemonics, Operand | Opcode(in HEX) | Bytes |
|---|---|---|
| LDA Address | 3A | 3 |
Let us consider LDA 4050H as an example instruction of this type. It is a 3-Byte instruction. The initial content of memory address 4050H is ABH. Initially Accumulator content is CDH. As after execution A will be initialized with value ABH. Memory location 4050H will still remain with the content ABH. The results of execution of this instruction is as below −
| Before | After | |
|---|---|---|
| (4050) | ABH | ABH |
| A | CDH | ABH |
| Address | Hex Codes | Mnemonic | Comment |
|---|---|---|---|
| 2008 | 3A | LDA 4050H | A <- Content of the memory location 4050H |
| 2009 | 50 | Low order Byte of the address | |
| 200A | 40 | High order Byte of the address |
Here is the timing diagram of the instruction LDA 4050H
Summary − So this instruction LDA 4050H requires 3-Bytes, 4-Machine Cycles (Opcode Fetch, Memory Read, Memory Read, Memory Read) and 13 T-States for execution as shown in the timing diagram.
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