Clock-8086 bus cycle 1. CLOCK • Activities on the system bus is synchronized by the system clock • Activities include: - Reading from memory or / IO - Writing to memory /IO • Any read or write cycle is called a bus cycle (machine cycle) • 8086 ,a bus cycle takes 4 T states, where one T state is defined as the 'period' of the clock. When immediate is greater then 1, assembler generates several RCL xx, 1 instructions because 8086 has machine code only for this instruction (the same principle works for all other shift/rotate instructions). Algorithm: exit from REPE cycle; else exit from REPE cycle; example: open cmpsb.asm from c:emu8086examples Z: r : REPNE In this video i explain Instruction Set of 8086 Microprocessor and its classification .In my next coming video i will explain all Instruction Set in detail w 8088/8086 Effective Address (EA) Calculation. Task State Calculation. FLAGS - Intel 8086 Family Flags Register. MSW - Machine Status Word (286+ only) The Instructions. AAA - Ascii Adjust for Addition. AAD - Ascii Adjust for Division. AAM - Ascii Adjust for Multiplication. AAS - Ascii Adjust for Subtraction. Fetch cycle - The next instruction is fetched by the address stored in program counter (PC) and then stored in the instruction register. Differences between 8085 and 8086 microprocessor. 15, May 18. Addressing modes in 8085 microprocessor. 13, Apr 18. Architecture of 8085 microprocessor. When two operands are required for an instruction they are separated by comma. For example: REG, memory When there are two operands, both operands must have the same size (except shift and rotate instructions). For example: AL, DL DX, AX m1 DB ? AL, m1 m2 DW ? AX, m2 Some instructions allow several operand combinations. For example: The 8086 MOV instruction supports the following operands: The instruction MOV mem, mem is illegal. It is not possible to transfer data directly from one memory location to another. Therefore, both source and destination operands cannot be memory address. The MOV instruction does not affect any value in the flag register. IO-Mapped & Memory-Mapped , Modes of I/O Instructions, Isolated I/O Direct I/O Indirect I/O String IN and OUT, I/O Design in 8086, Switch Interface LED Interface, Simple Output Port using 74373 Latch , Simple Input Port using 74245 Trans-receive Tristate Buffer, Key Debouncing Circuits MPI_Lec_26 Download Lesson Intro Video In 8085 Instruction set, DCX SP instruction is used to decrement the SP contents by 1. DCX SP instruction is a special case of DCX rp instruction which decreases the content of the register pair. This instruction occupies only 1-Byte in memory. Let us consider that the initial content of SP is 4050H. When a processor executes a program, the instructions (1 or 2 or 3 bytes in length) are executed sequentially by the system. The time taken by the processor to complete one instruction is called the Instruction Cycle (IC). An IC consists of Fetch Cycle (FC) and an Execute Cycle (EC). Thus IC = FC + EC. It is shown in Figure 2. The instruction cycle (also known as the fetch-decode-execute cycle, or simply the fetch-execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage. 8086 AAS Instruction . In ASCII code subtraction of two decimal digits, we need to mask the "011"or 3 in