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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, 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, 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, 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, RRC stands for “Rotate Right Accumulator”. With the help of this instruction, we can rotate the Accumulator current content to the right by 1-bit position. The following Fig. will depict the rotation operation. In this right rotation, the least significant bit will come out from the Accumulator and will be copied to Cy bit in the flag register and also will be copied to the most significant bit position of the Accumulator. Notice that the Cy flag is not involved in the rotation, and it is only 8-bit rotation of Accumulator contents. ... Read More
In 8085 Instruction set, with the mnemonic POP, we can pop out 2-Bytes from the top of the stack through rp i.e. register pair e.g. BC, DE, HL or AF. Here AF is a register pair formed with Flag and Accumulator registers and also known as PSW (Processor Status Word). In PSW, Accumulator is the MS Byte, and Flags register is the LS Byte. Mnemonics, Operand Opcode(in HEX) Bytes POP B C1 1 POP D D1 1 POP H E1 1 POP PSW F1 1 In the above ... Read More
In 8085 Instruction set, PUSH rp instruction stores contents of register pair rp by pushing it into two locations above the top of the stack. rp stands for one of the following register pairs. rp = BC, DE, HL, or PSW As rp can have any of the four values, there are four opcodes for this type of instruction. It occupies only 1-Byte in memory. Mnemonics, Operand Opcode(in HEX) Bytes PUSH B C5 1 PUSH D D5 1 PUSH H E5 1 PUSH PSW F5 1 ... Read More
In 8085 Instruction set, SPHL is an instruction with the help of which Stack Pointer will get initialized with the contents of register pair HL. It is an indirect way of initializing the stack pointer. But it is not a very common and regularly usable instruction as well. It occupies only 1-Byte in memory, compared to the other instruction LXI SP instruction, which is 3-Bytes long used for initializing SP on the other hand. Due to this advantage, SPHL can be useful when SP is required to get initialized to a specific value a number of times in a program. ... Read More
The maximum length of a table name is 64 characters long according to MySQl version 8.0.12. Check your installed MySQL version. mysql> select version(); The following is the output. +-----------+ | version() | +-----------+ | 8.0.12 | +-----------+ 1 row in set (0.03 sec) We can check the maximum length of the table name at the time of creating it. If we give more than 64 characters, then it will not create a table and an error is thrown. Creating a table which has more than 64 characters of table name. mysql> ... Read More
In 8085 Instruction set, NOP is an instruction which is falling under Machine Control Instruction category. NOP is a mnemonic that stands for “No Operation”. This instruction does nothing during execution. Only it occupied 1-Byte of memory space and spends 4-Machine Cycles. Mnemonics, Operand Opcode(in HEX) Bytes NOP 00 1 In spite of the fact that it does nothing, still it has got many different applications. It is useful in the following cases − NOP instruction can be used to create small-time delay in the execution of the code. It is very ... Read More