Instruction Naming Conventions:
An instruction is a binary pattern designed inside a microprocessor to perform a specific function. The entire group of instructions, called the instruction set, determines what functions the microprocessor can perform. These instructions can be classified into the following five functional categories: data transfer (copy) operations, arithmetic operations, logical operations, branching operations, and machine-control operations.
Data Transfer Group:
The data transfer instructions move data between registers or between memory and registers.
MOV Move MVI Move Immediate LDA Load Accumulator Directly from Memory STA Store Accumulator Directly in Memory LHLD Load H & L Registers Directly from Memory 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
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 Pair
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
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
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