89C51 or AT89C51 is an 8-bit microcontroller and belongs to Atmel’s family . Pdf of AT89C51 datasheet & pin diagram are also available at Engineers. AT89CPI Microchip Technology / Atmel 8-bit Microcontrollers – MCU UNSAWN WAFER 21 MIL BACKGRIND 89C51 – 24MHZ, PDIP, IND TEMP datasheet. Disclaimer: Whilst information is supplied in good faith, we are not liable for any errors or omissions. Please consult the relevant Atmel datasheet. E&OE. Key.

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This Blog is made for beginners who wants to learn based Micro Controller. Starting from simple to microcobtroller interfacing techniques of various devices with Micro Controllers. Port 0 ; is a dual-purpose port on pins of the 1C. For larger designs with external memory, it becomes a multiplexed a8t9c51 and data bus. The pins, designated as P1. No alternate functions are as signed for Port 1 pins; thus they are used solely for interfacing to external devices.

AT89C51 Microcontroller

Port 3; is a dual — purpose port on pins Now coming to the other pin functions. PSEN; This is an output pin. VCC; Pin 40 provides supply voltage to the chip. GND; Pin 20 is the Ground pin. One side of each capacitor is connected to the ground as shown in this figure. ALE; address latch enable is microcontriller output pin a nd is active high.

When connecting an to external memory, port 0 provides both address and data. In other words, the multiplexes address and data through microcontrollet 0 to save pins. Registers; In the CPU, registers are used to datasheeg information temporarily.

That information could be a byte of data to be processed, or an address pointing to the data to be fetched. The vast majority of 89C51 register an address pointing to the data to be fetched. The vast majority of 89C51 registers are 8-bit registers.

In the there is only one data type: With an 8-bit data type, any data larger than 8 bits must be broken into 8-bit chunks before it is processed.

All of the above registers are 8-bits, except DPTR and the program counter. The accumulator, register A, is used for all arithmetic and logic instructions. All the registers of 89C51 are. However, your links for the tutorials no longer work. Could you pls upload them again? Learn For Beginners. Now let us talk about this popular chip. It has on chip ROM in the form of flash memory. This is ideal for fast development since flash memory can be erased in seconds compared to the twenty minutes or more needed for the For this reason the AT89C51 is used in place of the to eliminate the waiting time needed to erase the chip and thereby speed up the development time.


Notice that in flash memory you must erase the entire contents of ROM in order to program it again.

This erasing of flash is done by the PROM burner itself. See the atmeo table for its specs The block diagram shows the internal structure of the microcontroller AT89C51; Pin description of this MCU can be seen in the following diagram; Port 0 ; is a dual-purpose port on microcontrloler of the 1C.

One side of each capacitor is connected to the ground as shown in this figure; EA; The family members, such as the89C51, or DS All come with on-chip ROM to store programs. In such cases, the EA pin is connected to VCC for giving power to save and erase program from the memory.

When this signal is brought high for a least two machine cycles, the internal registers are loaded with appropriate at89c5 for an orderly system start-up. For normal operation, RST is low. Figure shows permanent connections of Reset Pin.

ATMEL 89C51 | AT89C51 Microcontroller Pin Diagram & Description

All the registers of 89C51 are; Timers; Both timer 0 and timer 1 are 16 bits wide. Since the 89C51 has an 8-bit architecture, each bit timer is accessed as two separate registers of low byte and high byte. Each timer is discussed separately. Timer 0 Register; The bit register of time 0 is accesses as low byte and high byte.

The low byte catasheet is called TL0 timer 0 low byte and the high byte register is referred to as th0 timer 0 high byte. These registers can also be read like any other register. Timer 1 Register; Timer 1 is also 16 bits, and its bit register is split into two bytes, referred to as TL1 timer 1 low byte and TH1 timer 1 high byte.

These registers are accessible in microocontroller same way as the registers of timer 0. TMOD is an 8-bit register in which the lower 4 bits are set aside for timer 0 and the upper 4 bits are set aside for timer 1. In each case, the lower 2 bits are used to set the timer mode and the upper 2 bits to specify the operation.


Mode 2 Programming; The following are the characteristics and operations of mode 2. Then the timer must be started. This is just like mode 1. It counts up until it reaches its limit of FFH. If we are using timer 0, TF0 goes high; if we are using timer 1, TF1 is raised. To repeat the process, we must simply clear TF at89d51 let datasheeet go without any need by the programmer to reload the original value.

This makes mode 2 and auto-reload, in contrast with mode 1 in which the programmer has to reload TH and TL.

It must be emphasized that mode 2 is an 8-bit timer. However, it has an auto-reloading capability in auto reload. TH is loaded with the initial count and a copy of it is given to TL. This reloading leaves TH unchanged, still holding a copy of original value. This mode has many applications, including setting afmel baud rate in serial communication.

Atmmel can be accessed like any other register datasehet the 89C The moment a byte is written into SBUF, it is framed with the start and stop bits and transferred serially via the TxD pin. Similarly, when the bits are received serially via RxD, the 89C51 deframes it by eliminating the stop and start bits, making a byte out of the data received, and then placing tamel in the SBUF.

Some baud rates are shown below: Set by hardware at the beginning of the stop bit in mode1. Must by cleared by software. Set by hardware halfway through the stop bit time in mode1.

Must be cleared by software. The rest must be accessed in byte format. They are addressed as 0 to in decimal or 00 to 7FH. Posted by Fani at 4: Anonymous August 26, at 3: Newer Post Older Post Home.

Atmel AT89C51

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