Unit 2 Complete Notes.pdf

Pin diagram 8085a
MVI A, 80H2 byte
MVI B, 76H
Hex code45H, 80H
46,76
Store in memory
0000H 45H
0001H 80H
0002H 46H
0003H 76H

0004H
Addressing modes of 8085

Various ways of specifying the operands in the instruction
are called addressing modes. 8085 supports five different
types of Addressing mode.
MVI A, 80H
1.Register Addressing mode: instructions in which
operand is moving from register to register are called
register addressing mode.
Ex: MOV A, B
BA data move from B to A
Ex: ADD C, ADD B, ADD H
A+CA
If we want to add B & C
MOV A, B
ADD C
2.Immediate Addressing mode: when operand is given
in the instruction directly, then the instruction is a
example of Immediate Addressing mode.
MVI A, 75H=2 byte

MVI C, 45H
MVI H, 7AH
rp register pair (B, D, H).
LXI rp, 16 bit data
Ex: LXI B, 45ACH=3 byte
B=45H, C=ACH
3.Direct Addressing mode: When the address of the
operand is given in the instruction directly then in
that instruction Direct Addressing mode is used.
0014H 45H
054CH 96H
2200H 6BH
LDA 0014H
MOV B, A
A=45H
4.Indirect Addressing mode: When the address of the
operand is given in the instruction indirectly then in
that instruction indirect Addressing mode is used.
Assume reg B=05H & reg C=4CH
MVI r, 8bit data
MOV rd, rs
LDAX rp
LDAX B
Register pair BC=054CHdata96H

A=96H
5.Implied Addressing mode: In instructions where
operand is available in the opcode, then those
instructions are the example of Implied Addressing
mode.
Ex. CMAcomplement accumulator
A=7CH0111 1100
1000 0011
Data Transfer operations (MOV, MVI, OUT, IN)
1.Byte=? (1, 2, 3)
2.Machine cycle used in an instruction=? (1, 2, 3, 4,
5)no. of operations performed by microprocessor
3.T-states used in an instruction=? (4, 7, 10, 13, 16)
In some special cases T states will be (6, 18)
Userwrite in assemblyconvert into hex
codestore in memory
Microprocessor taskfetchdecodeexecute
Operation T-states used
OF 4, 6(in some special case)
MR 3
MW 3
IOR 3
IOW 3

OF, MR, MR, MWTstates13
r= A, B, C, D, E, H, L, M
Data Transfer operations (MOV, MVI, IN, OUT)
1.MOV rd, rs
ASSUME (B=45H, C=A1H)
Ex: MOV B, C (CB)
B= A1H, C=A1H
BYTE: 1
M/C: 1 (OF)
T: 4
HA
MOV A, H (register addressing mode is used)
2.MVI r, 8-bit data
B=45H
MVI B, 45H
BYTE: 2

M/C: 2(OF, MR)
T: 7
3.IN 8-bit address
EX: IN 80H
BYTE: 2
M/C: 3 (OF, MR, IOR)
T: 10
4.OUT 8-bit address
OUT 7CH
BYTE: 2
M/C: 3 (OF, MR, IOW)
T: 10

Machine control operation:
1.HLT:1 byte, M/c=1, T=5
2.NOP: no operation: 1 byte, M/c=1, T=4
0001 45
0002 46
0003 NOP
0004 45
0005 12
0006 45
Arithmetic operations: ADD, ADI, SUB, SUI,
INR, DCR
1.ADD r: if we want to add the data of A & B
ADD B (A+BA)
if we want to add the data of A & H
ADD H (A+HA)
Byte: 1
M/C:1
T:4
Flags affected: S, Z, AC, P, CY

EX: assume we have two data 4C & 2D, add these
data & store the result in reg H.
Program:
MVI A, 2DH
MVI B, 4CH
ADD B
MOV H, A
HLT
Ex2: Read from (1st
input device) 80H & (2nd
input
device) 81H, then add both the data & display the
result into output device (45H).
Program:
IN 80H
MOV B, A
IN 81H
ADD B
OUT 45H
HLT
2.ADI 8-bit data
Ex: ADI 76H
(A+ 76HA)
Byte: 2
M/C: 2
T: 7

3.SUB r: (A-rA)
EX: A-C
SUB C
Byte: 1
M/C: 1
T: 4
4.SUI 8 bit data
ASSUME A=4A
SUI 12H
4A-12A
Byte: 2
M/C: 2
T: 7
5.INR r
EX: H=4DH

INR H
H=4EH
Byte: 1
M/C: 1
T: 4
Flags affected: S, Z, AC, P
CY will not affected by INR
A=FFH
INR A
FF+1
6.DCR r
B=8AH
DCR B
B=89H
Byte: 1
M/C: 1

T: 4
Flags affected: S, Z, AC, P
CY will not affected by DCR
Logical instructions
Logic Operations (ANA, ANI, ORA, ORI, XRA, XRI)
1. ANA r
ANA B (logical AND operation between A, result goes
to A)
Ex: A=48H, B=A6H
ANA B
A=00H
B=A6H
Flags:

Byte: 1
M/C: 1
T: 4
ANI 8-bit data
ANI 7FH
Byte: 2
M/C: 2
T: 7
ORA r

Byte: 1
M/C: 1
T: 4
ORI 8 bit data
Byte: 2
M/C: 2
T: 7
XRA r
Byte: 1
M/C: 1
T: 4

XRI 8 bit data
Byte: 2
M/C: 2
T: 7
Programs
MOV, MVI, IN, OUT
ADD, ADI, SUB, SUI, INR, DCR
ANA, ANI, ORA, ORI, XRA, XRI
PROG1: B=7CH, D=56H add these data & store the result in reg H.
MOV A, B
ADD D
MOV H, A
HLT
PROG2: READ DATA FROM INPUT DEVICE 80H & 81H, LOGICAL
OR BOTH THE DATA & DISPLAY THE RESULT AT OUTPUT 83H.
PORG3: SWAP THE DATA OF REG H & L.
Branch operation (JMP, CALL, RESTART)

Prog: wap to logically XOR the input data 4DH &
2CH. Show the result in output of address 83H. Also
show the status of flags.
Prog: wap to subtract to 8 bit numbers stored in
B=ACH & C=69H. Store the result in reg E. Also show
the status of flags.
ACH1010 1100
69H 0110 1001
CALL instruction:
CALL 16 bit address
JMP 2000H (PC=2000H)
CALL 2000H(PC=2000H)
We jump to subroutine with a CALL instruction.
Subroutine: is a group of instructions written separately
from the main program.

Unit 2 Complete Notes.pdf

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Unit 2 Complete Notes.pdf