An instruction is a binary pattern designed to perform a specific function. The list of entire instructions is called the instruction set. The instruction set determines what function the microprocessor can perform.
The following notations are used in the description of the instructions:
R = 8085 8-bit registers (B, C, D, E, H, L)
M = memory register (location) pointed by value HL
Rs = register source
Rd = register destination (B, C, D, E, H, L)
Rp = register pair (BC, DE, HL)
( ) = contents of
The 8085 instruction set can be classified into the following five categories:
1. Data Transfer (copy) Instructions
These instructions perform the following six operations:
- Load 8-bit number in a register.
- Load 16-bit number in a register pair.
- Copy from register to register.
- Copy between register and memory.
- Copy between I/O and accumulator.
- Copy between registers and stack memory.
MVI R, 8-bit
MOV Rd, Rs
LXI Rp, 16-bit
OUT 8-bit
IN 8-bit
LDA 16-bit
STA 16-bit
LDAX Rp
STAX Rp
MOV R, M
MOV M, R
2. Arithmetic Instructions
The frequently used arithmetic operations are: Add, Subtract, Increment (add 1), Decrement (subtract 1)
ADD R
ADI 8-bit
ADD M
SUB R
SUI 8-bit
SUM M
INR R
INR M
DCR R
DCR M
INX Rp
DCX Rp
3. Logical and Bit Manipulation Instructions
These instructions include the following operations: AND, OR, X-OR, Compare, Rotate bits
ANA R
ANI 8-bit
ANA M
ORA R
ORI 8-bit
ORA M
XRA R
XRI 8-bit
XRA M
CMP R
CPI 8-bit
4. Branching Instructions
The following instructions change the program sequence.
JMP 16-bit
JZ 16-bit
JNZ 16-bit
JC 16-bit
JNC 16-bit
CALL 16-bit
RET
5. Miscellaneous Instructions
There are a number of instructions related with data transfer among the register, the stack operation instructions and interrupt operations of 8085 MP which are kept in this group. They are:
PUSH, POP
EI, DI
6. Machine Control Instructions
These instructions affect the operation of the processor.
HLT, NOP
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