Found 558 Articles for Microprocessor

In 8085 Instruction set, there is another mnemonic RAL, which stands or Rotate Accumulator Left and also involving Cy flag in rotation. It rotates the Accumulator contents to the left by 1-bit position. The following Fig. is depicting the execution logic of the instruction.From the Fig. we can see that the due to left rotation the bit which is coming out from the most significant place will be copied to the Cy flag bit. And the previous Cy bit will be moved to least significant bit place of the Accumulator. Thus it is a 9-bit rotation of Accumulator and Cy ... Read More

In 8085 Instruction set, there is one mnemonic RLC stands for “Rotate Left Accumulator”. It rotates the Accumulator contents to the left by 1-bit position. The following Fig. shows the operation explicitly. In this fig. it has been depicted that the most significant bit of the Accumulator will come out and left rotate will create an empty space at the least significant bit place and this come out bit will be copied at the empty bit place and also on the Cy bit in the flag register. Thus, Cy flag gets a copy of the bit moved out ... Read More

In 8085 Instruction set, CPI is a mnemonic that stands for “ComPare Immediate with Accumulator” and here d8 stands for any 8-bit data or 1-Byte data. This instruction is used to compare Accumulator with 8-bit immediate data. The result of the comparison will be stored in an internal register not accessible to the programmer. As this internal register is not a GPR (General Purpose Register), so not accessible through any mnemonics. Actually this 8-bit data will get deducted from Accumulators present content and result thus produced will be stored in the internal register. All the flags are affected based on ... Read More

In 8085 Instruction set, CMP is a mnemonic that stands for “CoMPareAccumulator” and hereR stands for any of the following registers, or memory location M pointed by HL pair. R = A, B, C, D, E, H, L, or M This instruction is used to compare contents of the Accumulator with given register R. The result of compare operation will be stored in the Temp register. Temp is not a GPR (General Purpose Register) but an internal register that is not accessible to the programmer. Actually R register’s content will get subtracted from Accumulators content and difference value ... Read More

In 8085 Instruction set, STC stands for “SeT the Carry flag”. It sets the cy flag to the 1 state, immaterial of its earlier value. It performs set operation on the cy flag, and the result is stored back in the cy flag. Mnemonics, Operand Opcode(in HEX) Bytes STC 37 1 The result of execution of this instruction has been depicted in the following tracing table − Before After (Cy) 1 1 (Cy) 0 1 Address Hex Codes Mnemonic Comment ... Read More

In 8085 Instruction set, CMC stands for “CoMplement the Carry flag”. It performs complement operation on the cy flag, and the result is stored back in the cy flag. Mnemonics, Operand Opcode(in HEX) Bytes CMC 3F 1 The result of execution of this instruction has been depicted in the following tracing table − Before After (Cy) 1 0 Address Hex Codes Mnemonic Comment 2001 3F CMC Complement of Cy when Cy=1 The timing diagram against this instruction CMC execution is as follows − Summary − So this instruction CMC requires 1-Byte, 1-Machine Cycle (Opcode Fetch) and 4 T-States for execution as shown in the timing diagram.

In 8085 Instruction set, XRI is a mnemonic that stands for “eXclusive OR Immediate with Accumulator” and “d8” stands for any 8-bit data. This instruction is used to Ex-OR 8-bit immediate data with the Accumulator. The result of Ex-ORing will be stored in the Accumulator overwriting its previous content. As it is a Logical instruction, so S, P, and Z flags are affected based on the result thus produced. Cy and AC are reset to 0. It occupies 2-Bytes in memory during execution. Mnemonics, Operand Opcode(in HEX) Bytes XRI Data EE 2 Let ... Read More

In 8085 Instruction, XRA is a mnemonic that stands for “eXclusive OR Accumulator” and “R” stands for any of the following registers, or memory location M pointed by HL pair. R = A, B, C, D, E, H, L, or M This instruction is used to Ex-OR contents of R with the Accumulator. The result of Ex-OR operation will be stored in the Accumulator. As R can have any of the eight values, there are eight opcodes for this type of instruction. It occupies only 1-Byte in memory. Mnemonics, Operand Opcode(in HEX) Bytes ... Read More

In 8085 Instruction set, ORI is a mnemonic that stands for “OR Immediate with Accumulator” and “d8” stands for any 8-bit data. This instruction is used to OR 8-bit immediate data with the Accumulator. The result of ORing will be stored in the Accumulator itself. As it is a logical instruction, the S, P, and Z flags are affected based on the result. Cy and AC are reset to 0. It occupies 2-Bytes in memory. Mnemonics, Operand Opcode(in HEX) Bytes ORI Data F6 2 Let us consider ORI CDH as an example instruction ... Read More

In 8085 Instruction set, ORA is a mnemonic, which stands for “OR Accumulator” and “R” stands for any of the following registers, or memory location M pointed by HL pair. R = A, B, C, D, E, H, L, or M This instruction is used to OR contents of R with the Accumulator. The result of OR operation will be stored back in the Accumulator. As R can have any of the eight values, there are eight opcodes for this type of instruction. It occupies only 1-Byte in memory. Mnemonics, Operand Opcode(in HEX) Bytes ... Read More