Microchip PIC32 Assembly Language Programming

Duration: 5 Days

Course Background

A knowledge of assembly language programming is a key skill for small embedded systems application developers. Not only does an understanding of the microcontroller instruction set help with debugging, it can be used to optimise code in resource constrained systems. It is also an important skill to have when implementing applications that are a mix of assembler and C code and when implementing low level device drivers. The Microchip 32 bit Microcontroller family with its MIPS architecture has an instruction set based on the original MIPS instruction set. The PIC32 processor core is based on the M4K core from MIPS Technologies. It supports a 16 bit instruction mode (MIPS16e) for more compact code. It also supports User and Kernel modes of operation which are especially useful when implementing and operating system, and has a multiply-divide unit.

This course will cover techniques for modular programming in assembler and the structured use of macros. It should also be of use to those teaching or developing computer science courses who will be delivering a module on more advanced microprocessor architectures, instruction sets and programming at the level of instruction sets.

Laboratory Workshops

Program object code into a target PIC32 microcontroller using MPLABX and ICD3
Create, build and debug new assembly language projects using MPLABX and ICD3
Use the MPLAB X Simulator to simulate and debug code prior to programming it into a target device
Understand the components of an assembly source file
Setting the PIC32 configuration options appropriately for the target system
Use digital I/O ports to interact with the outside world
Manipulating data memory using direct and indirect addressing
Create time delays using software loops and hardware timers
Writing code for interrupt handling and stack manipulation
Take advantage of interrupts to handle events in the background
Jump and call routines across pages in program memory
Use of PC-relative addressing to implement look-up tables
Implementing robust design techniques to protect against malfunctions

Course Prerequisites and Target Audience

Basic knowledge of programming and working with PC tools is assumed. Attendees are also expected to have a working knowledge of number systems decimal, octal, hexadecimal and binary and basic logic operations such as AND, OR, Exclusive OR and NOT. An appreciation of basic approaches to structured programming would also be helpful.

Course Outline

Microchip Overview

Market profile
product range
key advantages and support network

Overview of Development Tools

Microchip development software: MPLABX and associated tools
Microchip In-Circuit Debugger (ICD3) and In-Circuit Emulator (ICE) hardware
Device programmers, and the design option of In-Circuit Serial Programming (ICSP)
Demonstration boards and kits
Third-party development tools

The PIC32 Architectures and Instruction Set

The difference between a microcntroller and a microprocessor
Harvard versus Von Neumann architecture
Organisation of program and data memory
RISC architecture with multiple working registers
Op-codes and addressing modes: immediate, direct and indirect
On-chip peripherals and interrupts
Classes of operations performed by op-codes
The System Clock
Resets and Reset circuits
PIC32 I-side and D-side buses

The PIC32 processor architecture and Instruction Set Details

Understanding microcontroller pinouts and schematic diagrams
The PIC32 Microcontroller Instruction Sets

Load and Store Instructions
Computational Instructions
Jump and Branch Instructions
Miscellaneous Instructions
Coprocessor Instructions

Understanding PIC32 Microcontroller Addressing Modes

Immediate I-type CPU instructions
Jump J-type CPU instructions
Register Indirect Addressing
Registered R-type CPU instructions

Special Function Registers and Ports

The need for Special Function Registers
CP0 Registers - Coprocessor0 Interface - Status and Control Information

HWREna
BadVAddr
COUNT Register
COMPARE Register
STATUS Register
Intctl - Interrupt Control Register
SRSCtl Register - Control of GPR shadow sets
SRSMap Register and its use in interrupt handling
Cause and EPC (Cause of Last Exception and Program counter at last exception registers)
PRid and EBASE Registers (Processor identification and revision and Exception BASE address registers)
Config/Config1/Config2/Config3 (Configuration registers)
Debug/Debug2/ (Dbug control/exception status and EJTAG control)
DEPC - Program counter at last debug exception
ErrorEPC - Program counter at last error
DeSAVE - Debug handler scratchapad register
ErrorEPC - Program counter at last error

MIPS16e Mode and memory model
CPU Initialisation
PIC32 Memory Organisation

Control Registers
Memory Layout
Address Mapping
Bus Matrix
I/O Pin Control
Operation
Control Registers

Designing and implementing programs and applications

Requirements analysis
Describing algorithms using pseudo code (structured English)
Describing algorithms using flow charts
Basic template for an PIC32 assembler language application
Brief Introduction to Structured Analysis and Design using Ward-Mellor / Hatley Pirbhai / Jackson methodologies

Context Diagram
Flow diagrams
Control diagrams
Finite State Machines
Function mini-specs and pseudo code

Macros

Macros as pattern substitution
Macros with parameters
Macros and subroutines compared
Macros with parameters
Common Macro based patterns and idioms

Interrupts

The interrupt handling architecture of the PIC32
Interrupts and Event Driven Systems
Synchronous vs. Asynchronous Event Handling
Template for implementing an interrupt handler
Effective use of interrupt priorities in the PIC32

Digital Inputs and Outputs

Programming Digital Outputs
Programming Digital Inputs
Using Polling to detect input changes
Using Edge Triggered Interrupts to detect input changes
Debouncing
Programming a matrix keypad

Timers

How timers work
Timeout events and timeout handlers
Capture Compare
Pulse width modulation
Timers for generating periodic events
Timers and multi-tasking

Analog Inputs

Understanding Analog to Digital Conversion (ADC)
ADC architectures
Program templates for working with analog inputs
Foundations of signal processing
Use analog inputs to control and monitor

Serial buses and Protocols

RS232
I2C
SPI