SHLD and LHLD instruction

COMPUTER ORGANIZATION
it is very helpful instruction in CO to transferring data.

1. COMPUTER ORGANISATION TOPIC:DATA TRANSFER INSTRUCTIONS Group:- G2 BATCH:-B3 MADE BY:15CP032-SIDDHAPURA ROMIL 15CP018-AHALPARA KEVAL 15CP033-KAVAIYA HIREN 1

2. 8085 Microprocessor 2 The microprocessor is a programmable integrated device that has computing and decision making capability similar to that CPU of a computer. It is a multi- purpose,clock - driven, register-based electronic device.

3. LET’S BEGIN WITH MAIN DATA TRANSFER INSTRUCTIONS One of the primarily functions of microprocessor is copying data from source register to destination register. This copying function is labeled as data transfer instructions. In fact, contents of the source are not transferred but are copied into destination without modyfying the content of source. The previous contents of destination are replaced by the contents by the contents of the source. Several instruction are used to copy data which are listed below:- 3

4. LIST OF DATA TRANSFER INSTRUCTION MOV Rd,Rs :- Copies data from source register Rs to destination register Rd. MVI R,8-bit:- Loads the 8-bit of the second byte into the register specified. OUT 8-bit port address:- Sends the contents of the accumulator (A) to the output port specified in the second byte. IN 8-bit port address:-Accepts the data from the input port specified in second byte ,and loads into the accumulator. 4

5. “LHLD” INSTRUCTION LHLD stands for Load H and L Registers Direct . This instruction copies the contents of the memory location pointed by the 16-bit address in register L and copies the contents of the next memory location in register H. The contents of source memory locations are not altered. Flags:- The execution of LHLD instruction can not affect the flags. Example:- Assume memory allocation 1050H contains 30H and 1051H contains 32H.This instruction transfer memory contents to register pair HL. 5

6. For above example Instruction :- LHLD 1050H Hex code :- 2A 50 10 Memory contents before instruction:- Registers contents after instruction:- 6 1050 30 1051 32 H 32 L 30

7. 7 LHLD timing diagram

8. In 1 st Machine cycles, the 8085 microprocessor places the address of memory loaction on the address bus and fetches the opcode of LHLD instruction. The second machine cycle is read. In this machine cycle processor places the address of next incremented memory location and gets the low-order byte. The third machine cycle is also read. This machine cycle also perform the same as second machine cycle and gets the high-order byte instead of low-order byte. In the fourth machine cycle, contents of the memory location pointed out by 16-bit address copies into register L. In the fifth machine cycle, contents of the next memory location copies into register H. 8

9. Number of bytes used in instruction:- 3 bytes Total no. of machine cycles:- 5(F,R,R,R,R) Total no. of clock cycles:-16 Addressing modes:-Register direct 9

10. “SHLD” INSTRUCTION SHLD stands for store H and L Registers Direct. The contents of register L are stored in the memory location specified by the 16- bit address in the operand, and the contents of H registers are stored in the next memory location by incrementing the operand. Remember, the contents of the HL pair register are not altered. This is also a 3-byte instruction. The second byte specifies the low-order address and the third byte specifies the high-order address. 10

11. Flags:- No flags are affected. Example:-Assume the H and L registers contain 01H and FFH, respectively at memory location 1050H and 1051H. Instruction:- SHLD 1050H Hex code:- 22 50 10 Register contents before instruction:- Register and memory contents before instruction:- 11 H 01 L FF 1050 FF 1051 01 H 01 L FF

12. 12 SHLD timing diagram

13. In SHLD instruction, first 3 cycle is same as in described in LHLD instruction. In SHLD instruction, 4 th and 5 th cycle will be write cycle. So, in 4 th cycle, contents of the register L are stored in the memory pointed by the address in operand, and during 5 th machine cycle,contents of the register H are stored in next memory location. 13

14. Number of bytes used in instruction:- 3 bytes Total no. of machine cycles:- 5 (F,R,R,W,W) Total no. of clock cycles:-16 Addressing modes:- Register direct 14

15. 15 Thank you…!!!!