SIM Instruction use in 8085 microprocessor

This is the instruction used in 8085 microprocessor. it is " set interrupt mask" .

1. SIM INSTRUCTION By Ashish Mani

2. Introduction Format of SIM Instruction Explanation of Format of SIM Instruction CONTENTS:---

3. INTRODUCTION It is “Set Interrupt Mask” instruction. This instruction controls hardware interrupt of microprocessor It is the type of Implicit Addressing mode and of Single Byte instruction It has three different function:--- To set masking bit for interrupt RST7.5 , RST6.5 and RST5.5 interrupts. To reset RST7.5 flip-flop. To implement serial input output

4. SIM INSTRUCTION Harddware interrupt of Micropressor Format of SIM instruction

5. EXPLANATION OF SIM INSTRUCTION a) If D6 = SDE (serial data enable) = 1 , the binary bit in D7 is transferred to SOD (Serial output data) pin of microprocessor. b) If D6 = 0, then A7 bit is not transferred to SOD pin Hence data transfer is possible with SOD (serial output data) pin. If D4 = 1, RST 7.5 is reset. This is used to ignore RST 7.5 without servicing it. 3. If D3= MSE (Masking Set Enable) = 1, then the binary bit in D2, D1 and D0 flip-flop are transferred to masking flip-flop M7.5 , M6.5 , M5.5 flip-flop respectively. a) If D3= MSE= 1 , A2= 0/1, then after SIM instruction, M7.5 will be 0/1. Hence RST7.5 will be enabled/disabled respectively. b) If D3= MSE= 0, then A2, A1, A0 are not transferred , value of M7.5,M6.5, M5.5 will be X ,X, X.