Branching Group Instruction

Branching Group Instruction The branching instruction instructs the processor to go to a different memory location and the microprocessor continues excluding machine code from the new location. The branching instructions are the most powerful instructions because they allow the microprocessor to change the sequence of program either unconditionally or under certain test condition. The branching instructions are divided into following 3 groups: a. JUMP instruction b. CALL and RET instruction c. RESTART instruction The jump instruction specifies the memory location explicitly. They are 3 bytes instruction. Jump instruction categories into unconditional and conditional. 1. Unconditional Jump: 8085 includes unconditional JUMP instruction loop without depending any types of conditions. JMP 16-bit address e.g. JMP 4000H Memory location can also be specified with a label or name 2. Conditional Jump: The conditional JUMP instructions allow the microprocessor to make decision based on certain condition indicated by the flag. After logical and arithmetic operations flag are set or reset to reflect condition. The four flags namely CY, P, Z and S are used by JUMP instructions.

Arithmetic and Logic unit (ALU)

The ALU performs the computing function. It includes the accumulator, the temporary register, arithmetic and logic circuits and the flag register. The result in stored in the accumulator and the flags are ser or cleaned according to the result of operation.

Timing and Control Unit

This unit synchronizes all the microprocessor operation with the clock. The clock is symmetrical square wave signal that drives the CPU. The control circuitry and all the operations are drives by the clock signals.

Interrupt

The 8085 has 5 interrupt signals that can be used to interrupt a program execution. The various interrupt signals are INIR,RST 5.5, RST 6.5, RST 7.5 and TRAP.

Serial Input / Output Port

The 8085 has two signals to implement the serial transition transmission SID ans SOD. This two signals are used to transmitting the data serially.

Data and Address Bus

The 8085 has 8-bit data bus and hence 8-bit data can be transmitted parallel from and to a microprocessor. The 8085 has 16-bit address bus a memory address are of 16-bit.