8085 Instruction Set

Instruction Set

8085 instruction set consists of the following instructions:

• Data moving instructions.
• Arithmetic - add, subtract, increment and decrement.
• Logic - AND, OR, XOR and rotate.
• Control transfer - conditional, unconditional, call subroutine, return from subroutine and restarts.
• Input/Output instructions.
• Other - setting/clearing flag bits, enabling/disabling interrupts, stack operations, etc.

Data Transfer Group:

Data Transfer Group:
The data transfer instructions move data between registers or between memory and registers.

1. MOV Move
2. MVI Move Immediate
3. LDA Load Accumulator Directly from Memory
4. STA Store Accumulator Directly in Memory
5. LHLD Load H & L Registers Directly from Memory
6. SHLD Store H & L Registers Directly in Memory
   
   An 'X' in the name of a data transfer instruction implies that it deals with a register pair (16-bits):
   
   LXI Load Register Pair with Immediate data
   LDAX Load Accumulator from Address in Register Pair
   STAX Store Accumulator in Address in Register Pair
   XCHG Exchange H & L with D & E
   XTHL Exchange Top of Stack with H & L
   
   
   Arithmetic Group:
   The arithmetic instructions add, subtract, increment, or decrement data in registers or memory.
   ADD Add to Accumulator
   ADI Add Immediate Data to Accumulator
   ADC Add to Accumulator Using Carry Flag
   ACI Add Immediate data to Accumulator Using Carry
   SUB Subtract from Accumulator
   SUI Subtract Immediate Data from Accumulator
   SBB Subtract from Accumulator Using Borrow (Carry) Flag
   SBI Subtract Immediate from Accumulator Using Borrow (Carry) Flag
   INR Increment Specified Byte by One
   DCR Decrement Specified Byte by One
   INX Increment Register Pair by One
   DCX Decrement Register Pair by One
   DAD Double Register Add; Add Content of Register Pair to H & L Register
   Logical Group:
   This group performs logical (Boolean) operations on data in registers and memory and on condition flags.
   The logical AND, OR, and Exclusive OR instructions enable you to set specific bits in the accumulator ON or OFF.
   ANA Logical AND with Accumulator
   ANI Logical AND with Accumulator Using Immediate Data
   ORA Logical OR with Accumulator
   OR Logical OR with Accumulator Using Immediate Data
   XRA Exclusive Logical OR with Accumulator
   XRI Exclusive OR Using Immediate Data
   
   The Compare instructions compare the content of an 8-bit value with the contents of the accumulator:
   CMP Compare
   CPI Compare Using Immediate Data
   
   
   The rotate instructions shift the contents of the accumulator one bit position to the left or right:
   RLC Rotate Accumulator Left
   RRC Rotate Accumulator Right
   RAL Rotate Left Through Carry
   RAR Rotate Right Through Carry
   
   Complement and carry flag instructions:
   CMA Complement Accumulator
   CMC Complement Carry Flag
   STC Set Carry Flag
   
   Branch Group:
   The branching instructions alter normal sequential program flow, either unconditionally or conditionally. The unconditional branching instructions are as follows:
   JMP Jump
   CALL Call
   RET Return
   
   
   
   Conditional branching instructions examine the status of one of four condition flags to determine whether the specified branch is to be executed. The conditions that may be specified are as follows:
   NZ Not Zero (Z = 0)
   Z Zero (Z = 1)
   NC No Carry (C = 0)
   C Carry (C = 1)
   PO Parity Odd (P = 0)
   PE Parity Even (P = 1)
   P Plus (S = 0)
   M Minus (S = 1)
   
   Thus, the conditional branching instructions are specified as follows:
   Jumps Calls Returns
   C CC RC (Carry)
   INC CNC RNC (No Carry)
   JZ CZ RZ (Zero)
   JNZ CNZ RNZ (Not Zero)
   JP CP RP (Plus)
   JM CM RM (Minus)
   JPE CPE RPE (Parity Even)
   JP0 CPO RPO (Parity Odd)
   
   Two other instructions can affect a branch by replacing the contents or the program counter:
   PCHL Move H & L to Program Counter
   RST Special Restart Instruction Used with Interrupts
   
   Stack I/O, and Machine Control Instructions:
   The following instructions affect the Stack and/or Stack Pointer:
   PUSH Push Two bytes of Data onto the Stack
   POP Pop Two Bytes of Data off the Stack
   XTHL Exchange Top of Stack with H & L
   SPHL Move content of H & L to Stack Pointer
   
   The I/0 instructions are as follows:
   IN Initiate Input Operation
   OUT Initiate Output Operation
   
   The Machine Control instructions are as follows:
   EI Enable Interrupt System
   DI Disable Interrupt System
   HLT Halt
   NOP No Operation