PIC-18 Microcontroller
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This document provides an overview of the PIC-18 microcontroller. It describes the PIC-18's features such as its 8-bit architecture with 16-bit instruction sets, memory sizes including 256 bytes of EPROM and 2KB of SRAM. The document also discusses the PIC-18's addressing modes, memory organization with separate program and data memory spaces, and instruction pipelining capability.
PIC-18 Microcontroller
- 3. Microcontroller 8051 PIC ARM TYPES OF MICROCONTROLLER
- 4. Features of PIC-18 Microcontroller It is 8-bit Microcontroller. It has 16-bit Instruction sets. 256 byte of EPROM. 2 KB SRAM. 32 KB Flash Memory. It Operates at 40 MHz Crystal Oscillator. It has 10-bit A/D Converter. It supports Instruction Pipelining. It is implemented with nano watt Technology (low power consumption ).
- 5. PIN DIAGRAM OF PIC-18 MICROCONTROLLER
- 6. ARCHITECTURE OF PIC-18 MICROCONTROLLER
- 7. PIC-18 ADDRESSING MODES Register Direct : Use an 8-bit value to specify a data register. Ex:- movwf 0x20,A ; the value 0x20 is register direct mode Immediate Mode : A value in the instruction to be used as an operand. Ex:- addlw 0x10 ; add hex value 0x10 to WREG movlw 0x30 ; load 0x30 into WREG Inherent Mode : an implied operand. Ex:- andlw 0x3C ; the operand WREG is implied daw ; the operand WREG is implied Indirect Mode : A special function register (FSRx) is used as a pointer to the actual data register. Ex:- movwf INDFx (where x = 0,1,2,3)
- 8. PIC-18 MEMORY ORGANIZATION Data Memory and Program Memory are separated. Separation of Data memory and Program memory makes possible the the simultaneous access of data and instruction. Data memory are used as general purpose registers or special function registers. On-chip Data EPROM are provided in some PIC-18 MCUs
- 9. Separation of Data Memory and Program Memory Program Memory Space PIC-18 CPU 21-bit program address 16-bit instruction bus Data Memory Space 12-bit Register address 8-bit Data Bus Fig:- The PIC-18 Memory Spaces
- 10. PIC-18 DATA MEMORY It consist of General purpose register and Special function registers. Both are referred to as Data Registers. PIC-18 has 4KB Data Memory. Data Memory is Divided into Banks and each Bank has 256 bytes. General purpose registers are used to hold dynamic data. Special function register are used to control the Operation of Peripheral functions. Only on bank is active at any time. It implement access bank to reduce problem caused by bank switching. Access bank Consists of the lowest 96 bytes and the highest 160 bytes of the data memory space.
- 11. Fig : Data Memory map for PIC-18 Device
- 12. PROGRAM MEMORY ORGANIZATION The program counter (PC) is 21-bit long, which enables the user program to access up to 2MB program memory. After Power On it starts to execute the instruction from address 0. The Location 0x08 is reserved for high-priority interrupt service routine. The Location 0x18 is reserved for low-priority interrupt service routine. Up to 128 KB of Program Memory is inside the MCU chip. Rest Part of the program memory is located outside of the MCU chip.
- 13. Fig: Program Memory Organization for PIC-18 Device
- 14. PIC-18 PIPELINING The PIC18 Divide most of the instruction execution into two stages: instruction fetch and instruction execution. Up to two instructions are overlapped in their execution. One instruction is inexecution fetch stage while the second instruction is in execution stage. Because of pipelining, each instruction appears to take one instruction cycle to complete. Fetch 2 Execute 1 Fetch 4 Fetch 3 Fetch 1 Execute 2 Execute 3 Execute sub_1Fetch sub_1 Flush TCY0 TCY1 TCY2 TCY3 TCY4 TCY5 Fig : An Example of Instruction Pipeline flow
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