Data Transfer Group Instruction , microprocessor 8085

a) Data transfer Group

It is the group of instruction in 8085 .this group of instruction copy data from a source location to destination location without modifying content of the source. The transfer of data may b e  between the register or between  the register  memory and memo rot vice versa or between te I/O device and accumulator . None of the instruction change the content flag .the instruction are as follows:.

MOV Move
MVI Move Immediate
LDA Load Accumulator Directly from Memory
LXI Load Register Pair with Immediate data

LDAX Load Accumulator from Address in Register Pair

STA Store Accumulator Directly in Memory
STAX Store Accumulator in Address in Register Pair

LHLD Load H & L Registers Directly from Memory
SHLD Store H & L Registers Directly in Memory

XCHG Exchange H & L with D & E
XTHL Exchange Top of Stack with H & L

a) Data transfer Group

Something you must know before going into it

We have studied about the register their pair in previous chapter, microprocessor architecture I will denote R for the register signally and register pair as Rp. Some revision here , that the registers can be used alone or as a pair so some instruction take register pair([BC][DE][HL])as their operand whereas other take only register( B C D E H L ) as their operand.

Also the concept of bits

          ‘0101’ count the no of 1’s and 0’s you will get the no. four so hat is four bits representation.

          ‘01010000’ no. of 1,s and 0 is 8 so it is 8 bit representation.

8 bits = 1 byte

16 bits =2 bytes

Let’s take 3040h, it’s a hex data and the binary of it is 0111 0000 so, it’s a 8 bit data

8085 assembler converts the 3040 to 8 bit binary value and give to microprocessor.

MOV Move

MVI Move Immediate
LDA Load Accumulator Directly from Memory
LXI Load Register Pair with Immediate data

LDAX Load Accumulator from Address in Register Pair

STA Store Accumulator Directly in Memory
STAX Store Accumulator in Address in Register Pair

LHLD Load H & L Registers Directly from Memory
SHLD Store H & L Registers Directly in Memory

XCHG Exchange H & L with D & E
XTHL Exchange Top of Stack with H & L

1)      MOV (Move)

a)      MOV move register instruction.

·         MOV Rd, Rs                

·         1 byte instruction

·         Carries data from source register (Rs) to another destination register (Rd).

·         Rd and Rs may be A,B,C D,E ,H,L.

·         Eg: MOV   H,A

                  Here ,The content of accumulator is transferred to H register.

                       If Accumulator contain data 20h than program below output as.

                         MOV   H, A

                           HLT             

                                  output

                                   A:20

                                   B: 00          C: J J

                                   D: 00           E: 00

                                   H:20            L:00

b)      Move to  memory from register

·         MOV M,Rs

·         Move the content of the specified register to the memory .Here memory is the location specified by content Of the HL pair registers.

Here we will study actually what M is .

Let [HL] pair contain data 2030 ,then the location 2030 is called as  memory(M) and let  B contains data 40h.If we have the instruction:

 MOV   M,B

Than 2030 location is filled by data in register B and it is summarized as output as:

Output

B: 20h

[2030]:20h

c)      Move to register from memory

·         MOV R,M

·         1 byte instruction

·         Moves the content of the memory location specified by HL pair to specified by HL pair to the specified by HL pair to specified register.

For Example : IF [HL] pair contain data 5060h then instruction MOV D,M transfer the data containing in address 5060  to the register D.

2)      MVI (Move immediate) 

·         MVI R,8 bit data

·         Loads the 8 bits data into the specified register

·         R may be A,B,C,D,E,H ,L

·         Eg: MVI B,20h

In this example the content of register C is moved to B and data in C will also be unchanged.

 If C has data 20h than 20h will be moved to register B.

·          MVI M,8 bit data

3)       LXI ( Load registers pair directly)

·         LXI Rp,2 bytes data

·         byte instruction

·         load immediate 16 bit data to the register pair

·         Rp may be B(BC),D(DE),H(HL),& SP

1^st byte op code

2^nd byte lower order data

3^rd byte higher order data

4)      MVI (Load memory immediately)

a)      MVI  Rd,8 bit data to the

·         Loads the 8 bit data to the register

·         E.g. MVI B,20h

In this example 20h data is loaded  to register B.

Output

B: 20h

b)      MVI M,8 bit data

·         byte instruction

·         loads the 8-bit data to the memory location whose address is specified by the content of the HL pair

                 Eg. MVI M,35H; [HL] ß35 H

In this example 35h is stored in the location specified by the data in register pair HL

If the content of register pair [HL] was 2020 then 35h is stored in memory location 2020

Here

5)      LDA Load accumulator direct

·         LDA 16 bit address

·         2 byte instruction

·         loads the accumulator with the content of memory location whose address is specified by

·         the 16 bit address

·         Eg.LDA 4035;Aß[4035]

In this example the data from the address 4030 will be loaded to the Accumulator.

·         Eg.LDA 4035;Aß[4124]

In this example the data from the address 4124 will be loaded to the Accumulator.

Let’s solve a question

Write program to load the data

6)      LDAX (Load accumulator indirect )

·         LDAX  Rp

·         1 byte instruction

·         Moves the content of the memory location pointed by the content of the register pair to  accumulator

LXI

·         E.g LDAX B; Aß[BC]

Let [BC] pair contains 2020, then the instruction ‘LDAX B ‘ stores the data containing in address pointed by register B(i.e. 2020)

7)      STA (Store accumulator content direct)

·         STA 16 bit address

·         2 byte instruction

·         Stores the content of accumulator to specified address

·         Eg STA FA00,[FA00]ßA;

 In this example the content of accumulator is stored in the address FA00.m

Let’s do a program

MVI   A,20h

STA   5050h

HLT

Here, ‘MVI A, 20h’ stores the 20h in accumulator, and STA stores the content of accumulator to to 5050.

OUTPUT

A:20

           [5050]:20

                  

8)      Store accumulator content indirect

·         STAX Rp;

·         1 byte instruction