1. EECE.3170 Microprocessor Systems Design I
Instructor: Dr. Michael Geiger
Spring 2016
Lecture 28:
PICkit introduction

2. Microprocessors I: Lecture 28
Lecture outline
Announcements/reminders
HW 7 to be posted today; due 4/20 by 1:00 PM
HW 8: Working with PICkits—groups of up to 4 (3 preferred)
Cannot check out kit without a group before 4/22
Due 4/29 by 1:00 PM
Will get extra points if HW submitted and PICkit returned early
10% by 11:00 AM, Friday, 4/22
5% by 1:00 PM, Monday, 4/25
Review
Sample programming sequences: delay, state machine
Today’s lecture: working with PICkit
Assembler directives
MPLAB IDE
Working with existing projects
Simulator
In-circuit debugging
Sample programs in assembly and C
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Microprocessors I: Lecture 28

3. Review: A Delay Subroutine
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Review: A Delay Subroutine
; ***********************************************************************************
; TenMs subroutine and its call inserts a delay of exactly ten milliseconds
; into the execution of code.
; It assumes a 4 MHz crystal clock. One instruction cycle = 4 * Tosc.
; TenMsH equ 13 ; Initial value of TenMs Subroutine's counter
; TenMsL equ 250
; COUNTH and COUNTL are two variables
TenMs
nop ; one cycle
movlw TenMsH ; Initialize COUNT
movwf COUNTH
movlw TenMsL
movwf COUNTL
Ten_1
decfsz COUNTL,F ; Inner loop
goto Ten_1
decfsz COUNTH,F ; Outer loop
goto Ten_1
return
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Microprocessors I: Lecture 28
Chapter 9

4. Review: Strategy to “Blink”
The LEDs are toggled in sequence - green, yellow, red, green, yellow, red…
Let’s look at the lower three bits of PORTD
001=green, 010=yellow, 100=red
The next LED to be toggled is determined by the current LED.
001->010->100->001->…
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Microprocessors I: Lecture 28

5. Coding “Blink” with Table Use
BlinkTable
movf PORTD, W ; Copy present state of LEDs into W
andlw B' ' ; and keep only LED bits
addwf PCL,F ; Change PC with PCLATH and offset in W
retlw B' ' ; (000 -> 001) reinitialize to green
retlw B' ' ; (001 -> 010) green to yellow
retlw B' ' ; (010 -> 100) yellow to red
retlw B' ' ; (011 -> 001) reinitialize to green
retlw B' ' ; (100 -> 001) red to green
retlw B' ' ; (101 -> 001) reinitialize to green
retlw B' ' ; (110 -> 001) reinitialize to green
retlw B' ' ; (111 -> 001) reinitialize to green
In calling program
call BlinkTable ; get bits to change into W
xorwf PORTD, F ; toggle them into PORTD
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Microprocessors I: Lecture 28

6. PIC microcontroller programming
Done through MPLAB IDE
Allows for generation of projects in assembly or in C
Options to generate initialization code
In-circuit debugger to view device state while hardware is actually running
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Microprocessors I: Lecture 28

7. PIC assembler directives
banksel label
Changes BSR to bank containing label
Example: banksel TRISC
cblock/endc
Used to define a block of variables
org address
Indicates starting address for block of code that follows
Address 0 in simple programs (initial PC value)
#include file
Typically used to include processor-specific definitions, macros
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Microprocessors I: Lecture 28

8. Example 1: Light single LED (.asm)
Start: banksel TRISC ;select bank1 bcf TRISC,0 ;make C0 an output banksel LATC ;select bank2 clrf LATC ;initialize the ; LATCH by ; turning off ; everything bsf LATC,0 ;turn on LED C0 (DS1) goto $ ;sit here forever! end
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Microprocessors I: Lecture 28

9. Microprocessors I: Lecture 28
Example 1 notes (.asm)
TRISC: controls state of Port C pins
TRISC bits = 1  corresponding pins are inputs
TRISC bits = 0  corresponding pins are outputs
LATC: used for writing data to Port C
Equivalent to writing to PORTC register
Convention: for input, read PORTC; for output, write LATC
Infinite loop at end
$ symbol—special label for current instruction
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Microprocessors I: Lecture 28

10. Example 1: Light single LED (C)
void main(void) { TRISCbits.TRISC0 = 0; // Pin 0 = // output LATC = 0; //clear all pins to 0 LATCbits.LATC0 = 1; // turn ON LED while(1) continue; }
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Microprocessors I: Lecture 28

11. Microprocessors I: Lecture 28
Example 1 notes (C)
Can access entire registers by name
To access individual bits, use form:
regnamebits.regname#
Example: TRISCbits.TRISC0 = 0;
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Microprocessors I: Lecture 28

12. Microprocessors I: Lecture 28
Running program
Choose target device under
File  Project Properties
Either use PICkit3 or Simulator
Compilation
Clean and Build
Make and Program Device (PICkit3 only)
Separate options required for debug configuration
Click arrow on right of button to build/make for debug
Window  PIC Memory Views
Allows you to view file registers and/or SFRs
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Microprocessors I: Lecture 28

13. Microprocessors I: Lecture 28
Final notes
Next time:
Working with delay
Reminders:
HW 7 to be posted today; due 4/20
HW 8: Working with PICkits—groups of up to 4 (3 preferred)
Cannot check out kit without a group before 4/22
Will get extra points if HW submitted and PICkit returned early
10% by 11:00 AM, Friday, 4/22
5% by 1:00 PM, Monday, 4/25
4/27/2019
Microprocessors I: Lecture 28