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PIC18 Peripherals

PIC18 Peripherals. PIC18F452/458 Peripherals –. Data ports – A 6-bit B 8-bit C 8-bit D 8-bit E 3-bit Timer/counter modules – 0 [8-bit], 1 [16-bit], 2 [8-bit], 3 [16-bit]. CCP/PWM modules [2] I 2C/SPI serial port USART [RS-232, RS-485] ADC [10-bit] with 10 way input multiplexer

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PIC18 Peripherals

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  1. PIC18 Peripherals

  2. PIC18F452/458 Peripherals – • Data ports – • A 6-bit • B 8-bit • C 8-bit • D 8-bit • E 3-bit • Timer/counter modules – 0 [8-bit], 1 [16-bit], 2 [8-bit], 3 [16-bit]

  3. CCP/PWM modules [2] • I2C/SPI serial port • USART [RS-232, RS-485] • ADC [10-bit] with 10 way input multiplexer • EEPROM [256 byte]

  4. PIC instruction set • PIC instruction set has a small no. of simple (RISC) instructions: • PIC16 series – 35 inst. coded into 14 bits • PIC18 series – 59 16… • PIC24 series – 71 24… Most instructions are executed in one instruction cycle that corresponds to 4 clock cycles. Hence, a PIC operating at 40 MHz clock frequency will have an instruction rate of 10 MIPS.

  5. Byte-oriented file register operations • Byte-oriented file register operations – ADDWF Add W and f  result in W or f CLRF clear f DECF decrement f MOVF Move contents of f to f or W

  6. Bit-oriented file register operations BCF clear bit in f BTFSC test bit in f; skip if clear

  7. Control instructions CALL call subroutine (funtion) RETURN return from subroutine (function) BRA branch unconditionally BNZ branch if not zero

  8. Literal instr. MOVLW move literal to W ADDLW add literal to W

  9. Status register • 8-bit status register – • N negative bit – result of arithmetic operation was negative • OV overflow bit – overflow occurred for signed arithmetic • Z zero bit • DC digit carry bit – carry out from 4th low order bit of result • C carry bit –carry out from MSB of result The bits of the status reg can be used for conditional branches, e.g., - BNZ branch if not zero - BOV branch if overflow

  10. CCS PIC compiler • Compiler – high-level language prog to machine instructions for the target processor • Cross-compiler – is a compiler that runs on a processor that is different from the target processor • E.g., CCS cross-compiler • Most embedded systems are now programmed using C/C++ lang.

  11. PCwith CCS compiler USBICD2 debugger  PIC system • Programs are edited and compiled to PIC machine instructions on a PC • PIC machine instructions are uploaded from PC to PIC system via the ICD2 debugger [e.g., microchip MPLAB ICD2] • Code is executed on the PIC system and can be debugged (break points, inspect variables, single step, etc.) using PC

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