The Instruction Set of 8086. 1. How many instructions are there in the instruction set of 8086? Ans. There are 117 basic instructions in the instruction set of 8086. (XLAT) data transfer instruction is shown in Fig.14.2. It can be used for say an ASCII to EBCDIC code conversion. Mnemonic Meaning Format Operation Flags affected . 28. The XLATB Instruction. Belongs to the family of x86 data transfer instructions. XLATB translates bytes The format is XLATB. To use xlat instruction, EBX should be loaded with the starting address of the translation table. AL must contain an index in to the table. Index value starts at zero. The instruction. Hey Chegger, 1) The operation performed by 8086 when it executes the XLAT instruction - XLAT: When XLAT command is used, the 8086 starts to translate a byte in AL with the help of a table in the memory. String manipulation instructions in 8086 microprocessor. String is a series of data byte or word available in memory at consecutive locations. It is either referred as byte string or word string. Their memory is always allocated in a sequential order. Instructions used to manipulate strings are called string manipulation instructions. 8086 AAS Instruction . In ASCII code subtraction of two decimal digits, we need to mask the "011"or 3 in upper nibbles to obtain result in a unpacked BCD form. The Adjust after Subtraction instruction (AAS) provides the correct unpacked BCD result without masking the "3". The AAS instruction checks the conent of AL register. The contents of the AH register are copied into the lower byte of the Data Transfer Instructions in 8086 flag register. PUSHF Instruction : Push flag register on the stack. This instruction decrements the stack pointer by 2 and copies the word in the flag register to the memory location (s) pointed by the stack pointer. Data transfer instructions in 8086 microprocessor. Data transfer instructions are the instructions which transfers data in the microprocessor. They are also called copy instructions. Following is the table showing the list of data transfer instructions: Here D stands for destination and S stands for source. D and S can either be register, data 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: shift all bits left, the bit that goes off is set to CF and previous value of CF is inserted to the right-most position. Example: 1 Instruction set of 8086 The instruction set of 8086 can be classified into following groups 1. Data transfer instructions 2. Arithmetic instructions 3. replaces a byte in the AL register with a byte pointed to by BX register in a look up table in memory Before executing XLAT instruction, the look up table is to be put into memory and the 1 Answer. LAHF Instruction in 8086: Load lower byte of flag register in AH. This instruction copies the contents of lower byte of 8086 flag register to AH register. STOSB instruction in 8086: The STOS instruction copies a byte from AL or a word from AX to a memory location in the extra segment. DI is used to hold the offset of the memory Instruction set of 8086 Microprocessor. 2 XLAT replaces contents of AL by contents of memory location with PA=(DS)0 +(BX) +(AL) = 03000H + 0100H + 0DH = 0310DH Thus (0310DH) (AL) 13 Arithmetic Instructions: ADD, ADC, INC, AAA, DAA Mnemonic Meaning Format Operation Flag