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Microprocessor Articles
Page 9 of 42
1's complement notation
This is one of the methods of representing signed integers in the computer. In this method, the most significant digit (MSD) takes on extra meaning.If the MSD is a 0, we can evaluate the number just as we would interpret any normal unsigned integer.If the MSD is a 1, this indicates that the number is negative.The other bits indicate the magnitude (absolute value) of the number.If the number is negative, then the other bits signify the 1's complement of the magnitude of the number.Some signed decimal numbers and their equivalent in 1's complement notations are shown below, assuming a word ...
Read More8051 Program to Subtract two 8 Bit numbers
Here we will see how to subtract two 8-bit numbers using this microcontroller. The register A(Accumulator) is used as one operand in the operations. There are seven registers R0 – R7 in different register banks. We can use any of them as the second operand.We are taking two number73H and BDH at location 20H and 21H, After subtracting the result will be stored at location 30H and 31H. AddressValue...20H73H21HBDH...30H00H31H00H...ProgramMOVR0, #20H;set source address 20H to R0 MOVR1, #30H;set destination address 30H to R1 MOVA, @R0;take the value from source to register A MOVR5, A; Move the value from A to ...
Read More8051 Program to Multiply two 8 Bit numbers
Now we will try to multiply two 8-bit numbers using this 8051 microcontroller. The register A and B will be used for multiplication. No other registers can be used for multiplication. The result of the multiplication may exceed the 8-bit size. So the higher order byte is stored at register B, and lower order byte will be in the Accumulator A after multiplication.We are taking two number FFH and FFH at location 20H and 21H, After multiplying the result will be stored at location 30H and 31H. AddressValue...20HFFH21HFFH...30H00H31H00H...Program MOV R0, #20H;set source address 20H to R0 ...
Read More8051 Program to Divide two 8 Bit numbers
Now we will see another arithmetic operation. The divide operation to divide two 8-bit numbers using this 8051 microcontroller. The register A and B will be used in this operation. No other registers can be used for division. The result of the division has two parts. The quotient part and the remainder part. Register A will hold Quotient, and register B will hold Remainder.We are taking two number0EH and 03H at location 20H and 21H, After dividing the result will be stored at location 30H and 31H. AddressValue...20H0EH21H03H...30H00H31H00H...ProgramMOV R0, #20H;set source address 20H to R0 MOV R1, #30H;set destination address ...
Read MoreInterfacing 8279 Keyboard with 8085 Microprocessor
Here we will see how 8279 Chip can be used to interface a matrix keyboard with 8085 microprocessors. This chip can be used either keyboard/display interfacing mode or as a strobed input port. But generally, it is used as keyboard interfacing.The keyboard interfacing schemes can also be divided into two modes. These modes are Decoded mode of operationEncoded mode of operationDecoded Mode of OperationIn this mode, the matrix keyboard can have only four rows. These four rows can be selected by using SL3-0 select lines. There are eight columns. These can be selected using RL7-0 these eight column lines. So there are ...
Read MoreInterfacing 8279 Display with 8085 Microprocessor
The Intel 8279 is used for keyboard interfacing but it can also be used for multiplexed 7-segment LED display interfacing. To display a character into 7-segment display we have to store 7-segment code in a display RAM location. The display RAM of this chip can store 16 bytes of data.Write to Display RAMTo write to the display RAM one special command is needed to be applied on the 8279 control port. The following pattern is showing the RAM command that is written to the control port of 8279.100AiAAAAThe first three bits are 100. It indicates ‘ Write to Display RAM’command. ...
Read MoreInterrupt handing in 8051
As we have seen there are five different interrupts in 8051. These interrupts are INT0, INT1, TO, T1, TI/RI.There are six states in each machine cycle. These states are S1 to S6. All of the interrupts are sampled at the end of state S5 of each machine cycle. When the instruction takes more than one machine cycle, then the samples are polled during the next machine cycle. When an interrupt flag is set at the S5 of the first machine cycle, then the polling cycle will find it. The interrupt system generates LCALL instruction to call appropriate ISS.There are some ...
Read MoreInterfacing 8251 USART with 8085 Microprocessor
The 8251 chip is Universal Synchronous Asynchronous Receiver Transmitter (USART). It acts as a mediator between the microprocessor and peripheral devices. It converts serial data to parallel form and vice versa. This chip is 28 pin DIP.The pin description of 8251A chipPinDescriptionD0 - D7parallel dataC/DControl register or Data buffer selectRDRead ControlWRWrite controlCSChip SelectCLKclock pulseRESETResetTxCTransmitter ClockTxDtransmitted dataRxCReceiver ClockRxDReceiver DataRxRDYReceiver ReadyTxRDYTransmitter ReadyDSRData Set ReadyDTRData Terminal ReadySYNDET/Synchronous Detect/BRKDETDetectBreakRTSRequest to send DataCTSClear to send DataTxEMPTYTransmitter EmptyVccVcc (5V)GNDGround(0V)Now let us see the functional block diagram of the 8251 chip.There are five different sections in this diagram. These sections are as follows −Read/ Write control logicTransmitter ReceiverData Bus ...
Read MoreEI and DI instructions in 8085
In 8085 is having five internal interrupt signals that correspond to the five external interrupt pins. And these interrupts are only recognized only when the internal interrupt signal is activated, the 8085 gets interrupted, provided higher priority internal interrupt signals are not active at the same time. The 8085 checks all these internal interrupt signals in the penultimate clock cycle of the last machine cycle of instruction.With in 8085, there is a flip-flop called IE flip-flop. Here IE stands for Interrupt Enable. 8085 interrupt system is disabled whenever this flip-flop is reset to the 0 states. That is, even if ...
Read MoreSIM and RIM instructions in 8085
In 8085 Instruction set, SIM (Set Interrupt Mask) and RIM (Read Interrupt Mask) instructions can perform mask and unmask RST7.5, RST6.5, and RST5.5 interrupt pins and can also read their status. In 8085 Instruction set, SIM stands for “Set Interrupt Mask”. It is 1-Byte instruction and it is a multi-purpose instruction. The main uses of SIM instruction are –Masking/unmasking of RST7.5, RST6.5, and RST5.5Reset to 0 RST7.5 flip-flopPerform serial output of dataMnemonics, OperandOpcode(in HEX)BytesSIM301When SIM instruction is executed then the content of the Accumulator decides the action to be taken. So before executing the SIM instruction, it is mandatory to initialize ...
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