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9/20/6 Lecture 21 -PIC Architecture 1
PIC Architecture
9/20/6 Lecture 21 -PIC Architecture 2
PIC Architecture Will now look at another architecture Look at the microcontroller company Step 1 – The programmers model
9/20/6 Lecture 21 -PIC Architecture 3
Philosophy of PIC Architecture Embedded processing is pervasive Electronic intelligence in is everyday products
Company Philosophy Have products that fit the problem Many systems can be automated using 8-bit
microcontrollers Much of product line is 8-bit
9/20/6 Lecture 21 -PIC Architecture 4
Reasons for pervasiveness? Competitive pressure Expanded functionality of products Provide differentiation in product from that of
competitor Cost competitive integrated solution Allow creation of new classes of products
9/20/6 Lecture 21 -PIC Architecture 5
Microcontroller Solution Microcontroller features
CPU – processing unit Non-volatile program memory Re-settable non-volatile data memory
(EEPROM) RAM for data storage Direct support for various input/output
9/20/6 Lecture 21 -PIC Architecture 6
Some typical applications Automotive air bag systems Remote control Handheld tools Appliances – coffee pot, mixer, stove, refrigerator,
dish washer, washer, dryer Major home systems – heating and cooling Cordless phones and cell phones Security systems TV, DVD player/recorder, DVR, PVR Sound system
9/20/6 Lecture 21 -PIC Architecture 7
Come in 4-bit through 32-bit 4-bit
Very inexpensive 8-bit
Still very cheap – often ~$1.00 per chip 16 and 32 bit
Priced at $6.00 to 12.00 each Evaluation of requirements, chip capability,
and cost come into design decision
9/20/6 Lecture 21 -PIC Architecture 8
Typical automotive use Engine control – 32-bit microcontroller
Fuel flow, fuel mixture, valve timing, throttle body opening, spark timing
Transmission control –16-bit microcontroller Audio system – 16-bit Antilock braking – 16-bit Up to fifty 8-bit microcontrollers for functions of
Wiper control Electric Mirrors Air Bags
9/20/6 Lecture 21 -PIC Architecture 9
Automotive today continued Up to fifty 8-bit microcontrollers for functions of
Wiper control Electric Mirrors Air Bags Fuel pump Speedometer Security system Climate control system Power windows …..
9/20/6 Lecture 21 -PIC Architecture 10
Microchip’s position
9/20/6 Lecture 21 -PIC Architecture 11
Microchip and microcontroller use
9/20/6 Lecture 21 -PIC Architecture 12
Microcontroller choice parameters Number of I/O pins Amount of program and data memory Speed Timer Resources Interrupt control Robustness Error recovery – watchdog timers Power, I/O expansion, math support
9/20/6 Lecture 21 -PIC Architecture 13
Block Diagram
9/20/6 Lecture 21 -PIC Architecture 14
PIC architecture is a “Harvard” architecture The Harvard Architecture
9/20/6 Lecture 21 -PIC Architecture 15
Feature of Harvard architecture Near all instructions are single instruction
word instructions Only one fetch per instruction
Instruction fetch and execute are pipelined so you can operate at near clock rate instructions per second
2 separate buses One for instructions and one for data
9/20/6 Lecture 21 -PIC Architecture 16
PIC Instruction pipelining What % of
time does 1st flow of execution occur??
9/20/6 Lecture 21 -PIC Architecture 17
Frequency of Branches On architectures such as the HP during the
normal flow of a program’s execution on 8 to 12 instructions are executed before a branch occurs.
(aside) Modern architectures can easily achieve above 90% correct branch prediction.
This can be factored into actual “speed” of the processor.