Instructions of 8085 can be classified on three basis: First Classification on basis of their byte length i.e. size of instruction. 1. 1-byte instructions 2. 2-byte instructions 3. 3-byte instructions Second Classification on basis of their addressing modes i.e. kinds of approaches to fetch and execute. 1. Register Addressing 2. Immediate Addressing 3. Direct Addressing 4. Register Indirect Addressing 5. Implicit Addressing There are five sets of instructions for 8085mp Programming: 1. Data Transfer group 2. Arithmetic group 3. Logical group 4. Branching group 5. Machine Control group
Syntax: CMC Byte: 1byte Addressing Mode: Implied Addressing Flag: Carry Working: 1. Microprocessor will allocate one byte for opcode for execution. 2. During the execution of the instruction microprocessor will complement or perform 1's complement on content of Carry flag. Example: CMC where [Cy] = set = 1 After execution of CMC [Cy] = 0
Syntax: ANI 8-bit Where 8- bit is an immediate operand data. Byte: 2byte Addressing Mode: Immediate Addressing Working: 1.This is 2 byte instruction. 2. Microprocessor will allocate first byte for opcode and second byte for immediate data. 3. During execution of this instruction, microprocessor will perform Logical ANDing operation between content of Accumulator and Immediate data. 4. S, Z and P are modified . Cy is reset(Cy=0) and Ac is set (Ac=1) . Example: ANI 22H where [A]= 11H After execution of ANI 22H [A] = 00H A= 11 = 0001 0001 = 22 = 0010 0010 A=00 0000 0000 FLAG= 01 0 1 0 0 0 0 = 50H
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