Microcontroller – PIC – 4
PIC types
PIC architecture
PIC microcontroller
• PIC  Peripheral Interface Controller
– by Microchip Technology
• These devices have been very successful in 8-bit
microcontrollers.
• Why?  Microchip Technology has continuously
upgraded the device architecture and added
needed peripherals to the microcontroller to suit
customers' requirements.
• The development tools [assembler and simulator]
are freely available at http://microchip.com
Low-end PIC architecture
• have limited program/code memory
• for applications requiring simple interface
functions and small program & data memories
• Some device nos.
– 12C5XX
16C5X
16C505
Mid-range PIC arc…
•
•
•
•
more number of peripherals,
more number of registers and
more data/program memory.
Some devices are
– 16C6X
16C7X
16F87X
• Program memory type is indicated by alphabet:
C = EPROM  OTM (one-time programmable)
F = Flash
RC = Mask ROM [cheapest, burnt while IC fabrication]
UV-EPROM
Mem. vs. Pins vs. Versions
Compare 8-bit PIC arch.
• Visit
http://www.microchip.com/pagehandler/enus/family/8bit/architecture/home.html
PIC CPU archi.
Baseline PIC® Microcontrollers
read
• Simple 33 (12-bit wide) instruction set for
ease of use and quick development
• 2K word (3 KB) addressable program memory
• 144 bytes RAM (max)
• 2 level hardware stack
• 1 (8-bit) file select register
• Multiple product options and easy migration
Mid-range PIC
read
•
•
•
•
•
•
•
35 (14-bit wide) instructions
8K word (14 KB) addressable program memory
46 bytes RAM (max)
8 level hardware stack
1 (9-bit) file select register
Hardware interrupt handling
Highly integrated feature set, including EEPROM,
LCD, mTouch™ sensing solutions and serial
communications
Enhanced Mid-Range PIC
read
•
•
•
•
•
•
•
49 (14-bit wide) instructions
32K word (56 KB) addressable program memory
4KB RAM (max)
16 level hardware stack
2 (16-bit) file select registers
Hardware interrupt handling with content save
Advanced feature set, multiple serial
communications and motor control capability
PIC18
read
K series
• Provides the highest performance with benchmark
nanoWatt XLP extreme low power consumption.
• 83 (16-bit wide) powerful C-optimized
• Up to 2 MB addressable program memory
• 4KB RAM (max)
• 32 level hardware stack
• 1 (8-bit) file select register
• Integrated 8x8 hardware multiply
• Highest performance 8-bit architecture
Why PIC is popular?
• Speed: Harvard Architecture, RISC
architecture, 1 instruction cycle = 4 clock
cycles.
• Instruction set simplicity: The instruction set
has 35 instructions for PIC16 (as opposed to
111 instructions for 8051).
Why PIC is popular?...
• Power-on-reset and brown-out reset.
• Brown-out-reset means when the power
supply goes below a specified voltage (say 4V),
it causes PIC to reset; hence malfunction is
avoided.
• A watchdog timer (user programmable) resets
the processor, if the software/program ever
malfunctions and deviates from its normal
operation.
Why PIC is popular?...
• PIC microcontroller has 4 optional clock
sources.
–
–
–
–
Low power crystal
Mid range crystal
High range crystal
RC oscillator (low cost).
• Programmable timers and on-chip ADC.
• Up to 12 independent interrupt sources.
Why PIC is popular?...
– EPROM/
– OTP[one-time programmable] ROM/
– Masked version/
– Flash memory option.
• I/O port expansion capability.
• Free assembler and simulator support from
Microchip at www.microchip.com
PIC CPU archi.
PIC Memory Organization
•
•
•
•
•
has 13 bits of program/code memory address.
Hence it can address up to 8k [213=8192] of program memory.
The program counter is 13-bit.
PIC 16C6X or 16C7X program memory is 2k or 4k.
While addressing 2k of program memory, only 11-bits are
required. Hence two MSBs of the program counter are
ignored.
• Similarly, while addressing 4k of memory, 12 bits are required.
Hence the MSB of the program counter is ignored.
– 2^10 = 1024
– 2^12=4096
– 2^14=16384
…
2^11 = 2048
2^13=8192
2^16=65536
Data mem. / RAM
Data memory (Register Files):
• Data Memory aka Register File.
• Register File consists of two components.
– General purpose register file (same as RAM).
– Special purpose register file (similar to SFR in 8051:
Special Function Registers (SFRs) of 128 bytes) – fixed
& every microcontroller must have them
• It consists of I/O ports and control registers
 Recall registers of 8086 & compare
• PIC18 has a max of 4096 bytes (4K) [2^12=4096]of
data RAM space.
• Size of special-purpose reg [SPR] is fixed
• Size of general-purpose reg [GPR] varies from
256 B to 4096 B.
• GPR is divided into banks of 256B each [more – ch.6]
Data mem map
PIC18 – I/O pins
• Can have from 16 to 72 pins – dedicated for
I/O
[more ch. 4]
PIC18 - peripherals
• All PIC18 family have the following standard
peripherals –
– ADC
– Timers
– USART [universal synchronous asynchronous
receiver transmitter] – it allows us to connect the
PIC18-based system to serial ports (e.g., COM port of the
IBM PC)
PIC µC peripherals
•
•
•
•
•
•
•
•
CAN- (Controller Area Network),
LIN- (Local Interconnect Network),
USB- (Universal Serial Bus),
I²C- (Inter-Integrated Circuit),
SPI- (Serial Peripheral Interface),
Serial or Ethernet Interface
ADC - Analog Digital Converter
USART- Universal Synchronous Asynchronous Receiver
Transmitter
29
Courtesy –
•
http://microchip.com
•
‘PIC Microcontroller and Embedded Systems, by MA Mazidi et al., Pearson, 2012