Microcontrollers Introduction to the PIC 8-bit Midrange Family ECE Senior Design 15 February 2017
Popular Microcontrollers 8051 Intel then Everyone (8-bit old) PIC Microchip (8, 16 & 32bit) AVR Atmel (8 & 32bit) MSP430 TI (low power 16-bit) ARM Cortex ARM Limited (32 bit) 68HCSxx Motorola/freescale-NXP (old) PSoC Cypress (M8C, 8051,ARM) Nios II / MicroBlaze Altera / Xilinx (sc) Blue = commonly used in Senior Design
What the does PIC stand for anyway? PIC Peripheral Interface Controller The original PIC was designed to be a Peripheral Interface Controller for 6502 microcontroller from Rockwell late 70's.
Why did we choose Microchip PIC Family of Microcontrollers? Free development software MPLAB IDE (Includes a Simulator) Low cost development hardware (Boards starting at $10) Devices are easy to obtain through distributors and can be sampled A wide range of devices are available with varying feature sets Microchip is in continuous development of new PIC devices Has a large online support community Wide acceptance in industry over 15 Billion units shipped (1B/yr)
Datasheet Feature Page 16F18324 Datasheet PIC16F18324 Processor Structure of the PIC16F18324 Device Pins for the PIC16F18324
Microcontroller Block Diagram
GPIO PIC16F18324 Port A (RA0, RA1, RA2, RA3, RA4, RA5) Port C (RC0, RC1, RC2, RC3, RC4, RC5)
Generic Port Structure
PORTA Register
TRISIA Register
LATA Register
ANSELA Register
Lighting an LED
Program Memory Map and Stack Reset Vector - 0000h Interrupt Vector - 0004h Program Memory - 4096 Stack Depth - 16
Data Memory (32 Banks total)
The W Register (working register) reg1, w ; Move a file registers contents into the W register addwf reg2, w ; Place result in W register Program Memory Program Address 13 Program Counter 14 Instruction Instruction Register Direct Addr. 7 File Registers Data Bus 8 Instruction Decode and Control ALU 8 W Register
The Status Register Program Memory Program Address 13 Program Counter 14 Instruction Instruction Register Direct Addr. 7 File Registers Data Bus 8 Instruction Decode and Control Status Register result 3 ALU 8 W Register
The Status bits Arithmetic Status of the ALU Reset Status WDT and PD
Pipelining of Instructions Most instructions Execute in a single Processor Cycle A Processor Cycle is 4 Clock Cycles Using a 4MHz oscillator each processor cycle is 1MHz This results in a 1us execution time
Non-Sequential Address Read Exception to the one processor cycle per instruction is for Branching operations The Pipeline will be broken on a non-sequential address read Branching instructions require two processor cycles to execute
Instruction Pipelining Pre-ed Instruction Executing Instruction movlw 0x05 - Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w
Instruction Pipelining Pre-ed Instruction Executing Instruction movwf REG1 movlw 0x05 Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 Execute 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w
Instruction Pipelining Pre-ed Instruction Executing Instruction call SUB1 movwf REG1 Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 T2 Execute Execute Time to execute normal instruction 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w
Instruction Pipelining Pre-ed Instruction Executing Instruction addwf REG2 call SUB1 Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 T2 T3 Execute Execute Execute 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w
Instruction Pipelining Pre-ed Instruction Executing Instruction PORTB,w call SUB1 Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 T2 T3 T4 Execute Execute Execute Flush Time to execute call instruction includes pipeline flush 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w
Instruction Pipelining Pre-ed Instruction Executing Instruction PORTB,w Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 T2 T3 T4 T5 Execute Execute Execute Flush 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w Execute
Instruction Pipelining Pre-ed Instruction Executing Instruction PORTC,w Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 T2 T3 T4 T5 Execute Execute Execute Flush T6 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w Execute Execute
Instruction Pipelining Pre-ed Instruction Executing Instruction addwf REG2 Instruction Cycles 1 2 3 4 Example Program MAIN movlw 0x05 movwf REG1 call SUB1 addwf REG2 T0 T1 T2 T3 T4 T5 Execute Execute Execute Flush T6 T7 51 52 53 54 SUB1 SUB2 PORTB,w PORTC,w Execute Execute Flush
Blinking an LED time wasting loop bad Initialize Main Call Count_Time Call Toggle_LED Goto Main Count_Time ToggleLED Kill some time Looping in here Change state of LED