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The PIC chip
PIC microcontrollers come with a range of specifications, in terms
of the size and types of memory included, internal file structure
and functions included. The following information refers to the
PIC16F84.
When buying a PIC chip the following information
is often given
Typical Chip specification:
All instructions are executed in a single cycle, except for program
branches which require two cycles. The device has a 1K-word flash,
68 bytes data RAM, 64 bytes data EEPROM and 13 I/O pins.
Memory Allocation
- Program
memory – a 1k block of memory (1024 separate
memory locations used to store the current program. Each
memory location
can store a 14 bit instruction. Blank data is represented
by 14 logic 1’s, or 3FFFh in hexadecimal.
- Data
memory – 64
memory locations, each 8 bits wide, used to store data
either needed by or resulting from the program.
This area has two sections. One contains Special Function
Registers, which control the operation of the device. The other area contains
General Purpose Registers, which can be used by the programmer
to store information generated by the program.
-
Working
register – a
one byte register in which most of the mathematical
and logic operations are carried out.
The two ports are bi-directional, meaning that either can be set
up to input or to output data.
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