Embedded systems/8051 microcontroller – wikibooks, open books to have an open world
PIN 9:
PIN 9 may be the reset pin which is often used to reset the microcontroller’s internal registers and ports upon beginning up. (Pin ought to be held high for just two machine cycles.)
PINS 18 & 19:
The 8051 includes a built-in oscillator amplifier hence we have to only connect a very at these pins to supply clock pulses towards the circuit.
PIN 9:PIN 9 may be the reset pin which is often used to reset the microcontroller’s internal registers and ports upon beginning up. (Pin ought to be held high for just two machine cycles.)
PINS 18 & 19:
The 8051 includes a built-in oscillator amplifier hence we have to only connect a very at these pins to supply clock pulses towards the circuit.
PIN 40 and 20:
Pins 40 and 20 are VCC and ground correspondingly. The 8051 nick needs +5V 500mA to operate correctly, however, there are lower powered versions such as the Atmel 2051 that is a scaled lower form of the 8051 which operates on +3V.
PINS 29, 30 & 31:
As described within the options that come with the 8051, this nick includes a built-in flash memory. To be able to program this we have to give you a current of +12V at pin 31. If exterior memory is connected then PIN 31, also known as EA/VPP, ought to be linked to ground to point the existence of exterior memory.
PIN 30 is known as ALE (address latch enable), which is often used when multiple memory chips are attached to the controller and just one of these must be selected.We’ll cope with this thorough within the later chapters.
PIN 29 is known as PSEN. This really is “program store enable”. To use the exterior memory it’s needed to supply the reduced current () on PSEN and EA pins.
Pin 29:
When we make use of an exterior ROM it must have a logic which signifies Micro controller to see data from memory.
Pin 30:
This Pin can be used for ALE that’s Address Latch Enable. When we use multiple memory chips this pin can be used to differentiate together.It’s activated periodically having a constant rate of just oneOrsixth of oscillator frequency.
This Pin also gives program pulse input during programming of EPROM.
Pin 31:
If we must use multiple recollections then by making use of logic 1 for this pin instructs Micro controller to see data from both recollections first internal and later on exterior.
Ports[edit]
You will find 4 8-bit ports: P0, P1, P2 and P3.
PORT P1 (Pins 1 to eight):
The main harbour P1 is really a general purpose input/output port that you can use for various interfacing tasks. Another ports P0, P2 and P3 have dual roles or additional functions connected together based on the context of the usage.The main harbour 1 output buffers can sink/source four TTL inputs.
When 1s are written to portn1 pins are pulled high through the internal pull-ups and can be used inputs.
PORT P3 (Pins 10 to 17):
PORT P3 functions like a normal IO port, but Port P3 has additional functions for example, serial transmit and receive pins, 2 exterior interrupt pins, 2 exterior counter inputs, read pins for memory access.
PORT P2 (pins 21 to twenty-eight):
PORT P2 may also be used like a general purpose 8 bit port when no exterior memory exists, but when exterior memory access is needed then PORT P2 will behave as a previous address bus along with PORT P0 to gain access to exterior memory. PORT P2 functions as A8-A15, as possible seen from fig 1.1
PORT P0 (pins 32 to 39)
PORT P0 can be used an over-all purpose 8 bit port when no exterior memory exists, but when exterior memory access is needed then PORT P0 functions like a multiplexed address and knowledge bus you can use to gain access to exterior memory along with PORT P2. P0 functions as AD0-AD7, as possible seen from fig 1.1
PORT P10:
asynchronous communication input or Serial synchronous communication output.
PIN 11:
Serial Asynchronous Communication Output or Serial Synchronous Communication clock Output.
Oscillator Circuits[edit]
The 8051 requires an exterior oscillator circuit. The oscillator circuit usually moment 12 MHz, even though the 8051 (based on which specific model) is capable of doing running at no more than 40 MHz. Each machine cycle within the 8051 is 12 clock cycles, giving a highly effective cycle rate at 1 MHz (for any 12 MHz clock) to three.33 MHz (for that maximum 40 MHz clock).
The oscillator circuit generates the time pulses to ensure that all internal operations are synchronized.
One machine cycle has 6 states. One condition is 2 T-states. Therefore one machine cycle is 12 T-states.
Time for you to execute an instruction is located by multiplying C by 12 and dividing product by Very frequency.
T=(C*12d)/very frequency
Resourse: https://en.wikibooks.org/wiki/Embedded_Systems/
