PIC16x84
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The PIC16C84 and PIC16F84 are microcontrollers in the PIC family of controllers, produced by Microchip Technology.
[edit] Description
The PIC16F84A is an improved version of the PIC16C84, and almost completely compatible, with better program security and using flash memory instead of EEPROM memory for program memory. The PIC16F84A has 68 bytes of RAM whilst the PIC16C84 has 36 bytes. Both versions feature a wide voltage range, low power consumption, internal timer, and PIC I/O controls.
Since the two chips are so similar they are often referred to by the term PIC16x84 (x is used as a wildcard when referring to chips).
PIC16F84 belongs to a class of 8-bit microcontrollers of RISC architecture. Its general structure is shown on the following map representing basic blocks. Program memory (FLASH)- for storing a written program. Since memory made in FLASH technology can be programmed and cleared more than once, it makes this microcontroller suitable for device development. EEPROM - data memory that needs to be saved when there is no supply. It is usually used for storing important data that must not be lost if power supply suddenly stops. For instance, one such data is an assigned temperature in temperature regulators. If during a loss of power supply this data was lost, we would have to make the adjustment once again upon return of supply.
Thus our device looses on self-reliance. RAM - data memory used by a program during its execution. In RAM are stored all inter-results or temporary data during run-time. PORTA and PORTB are physical connections between the microcontroller and the outside world. Port A has five, and port B has eight pins. FREE-RUN TIMER is an 8-bit register inside a microcontroller that works independently of the program. On every fourth clock of the oscillator it increments its value until it reaches the maximum (255), and then it starts counting over again from zero. As we know the exact timing between each two increments of the timer contents, timer can be used for measuring time which is very useful with some devices. CENTRAL PROCESSING UNIT has a role of connective element between other blocks in the microcontroller. It coordinates the work of other blocks and executes the user program
Applications
PIC16F84 perfectly fits many uses, from automotive industries and controlling home appliances to industrial instruments, remote sensors, electrical door locks and safety devices. It is also ideal for smart cards as well as for battery supplied devices because of its low consumption.
EEPROM memory makes it easier to apply microcontrollers to devices where permanent storage of various parameters is needed (codes for transmitters, motor speed, receiver frequencies, etc.). Low cost, low consumption, easy handling and flexibility make PIC16F84 applicable even in areas where microcontrollers had not previously been considered (example: timer functions, interface replacement in larger systems, coprocessor applications, etc.).
In System Programmability of this chip (along with using only two pins in data transfer) makes possible the flexibility of a product, after assembling and testing have been completed. This capability can be used to create assembly-line production, to store calibration data available only after final testing, or it can be used to improve programs on finished products.
Datasheet : [1]
[edit] History
The PIC16C84 was the first PIC microcontroller to feature a serial programming algorithm and EEPROM memory, both of which lend themselves to hobby use: only a simple and cheap programmer is required to program, erase and reprogram the chip. As PIC16C84 supplies became limited due to it being discontinued, the PIC16F84 became popular as an almost drop in replacement. New programming software was needed as the programming algorithm is different but the programming hardware required was the same.
The PIC16x84 microcontroller is a member of Microchip's 14-bit series (the instruction word size is 14 bits for all instructions), making the '84 a good development prototype for other similar but cheaper one-time-programmable 14-bit devices.
