Explore ATtiny Microcontrollers using C and Assembly Language: AVR Architecture and Programming

Introduction
	Broad Overview of this Book
	About the Targeted AVR Microcontrollers
	Primary Programming Software
	Why Learn Assembly Language?
	The Many Reasons for Learning Assembly Language
	C Programming
	Intended Audience
	Prerequisites
		Software Requirements
		Hardware Requirements
			A DIP Packaged ATtiny
			An Electronic Breadboard
			Programmer/Debugger
				Atmel-ICE Basic Kit
				Atmel-ICE Full Kit
				AVR Dragon
				AVRISP mkII
				Hobbyist USB Programmers
			Power Supply
			Jumper Links and Wires
			Electronic Components
			Optional Test Equipment
	Microchip, Atmel, Microchip Studio and Atmel Studio
	Accompanying Resources
	Let’s Get Started
Chapter 1 • Overview of ATtiny Microcontrollers
	1.1 ATtiny Microcontrollers
		1.1.1 8-Pin Devices
			1.1.1.1 ATtiny13 and ATtiny13A
			1.1.1.2 ATtiny25, ATtiny45 and ATtiny85
		1.1.2 14-Pin ATtiny24, ATtiny44 and ATtiny84
		1.1.3 20-Pin Devices
			1.1.3.1 ATtiny26
			1.1.3.2 ATtiny261, ATtiny461 and ATtiny861
			1.1.3.3 ATtiny2313 and ATtiny4313
		1.1.4 28-Pin Devices
			1.1.4.1 ATtiny48 and ATtiny88
			1.1.4.2 ATtiny28L and ATtiny28V
	1.2 Which ATtiny to Use
	1.3 Comparison of ATtiny Devices
	1.4 Summary
Chapter 2 • Hardware and Software Setup
	2.1 Install Microchip Studio
		2.1.1 Download Page and Software Version
		2.1.2 Newest Software Version
		2.1.3 Start the Installation
		2.1.4 Installation Steps
	2.2 8-Pin ATtiny Microcontroller LED Circuit
		2.2.1 Circuit Power Supply
		2.2.2 Decoupling Capacitor
	2.3 A First Assembly Language Program
		2.3.1 Start a New AVR Assembler Project in Microchip Studio
		2.3.2 LED Blink Assembly Code
		2.3.3 Build the Project
		2.3.4 Fix Any Build Errors
		2.3.5 Load the Program to the AVR Microcontroller
		2.3.6 Fault Finding
	2.4 A First C Program
		2.4.1 Start a New GCC C Executable Project in Microchip Studio
		2.4.2 LED Blink C Code
		2.4.3 Build the Project
		2.4.4 Fix Any Build Errors
		2.4.5 Load the Program to the AVR Microcontroller
		2.4.6 Fault Finding
	2.5 Summary
Chapter 3 • Basics of Assembly Language
	3.1 Mnemonics
	3.2 AVR Instruction Set
	3.3 Opcodes and Operands
	3.4 Assembly Language Comments
	3.5 LED Blink Program Operation
	3.6 Using the Debugger and Simulator
		3.6.1 Using the AVR Simulator and Debugger
		3.6.2 Using a Physical AVR Microcontroller and Debugger
		3.6.3 Putting an AVR Back into ISP mode
	3.7 Summary
Chapter 4 • Binary Numbers and Memory
	4.1 Bits and Bytes
		4.1.1 Counting in Binary
		4.1.2 Bytes and Nibbles
	4.2 Weighted Number Systems
		4.2.1 Weighted Decimal Numbers
		4.2.2 Weighted Binary Numbers
	4.3 Hexadecimal Numbers
		4.3.1 Counting in Hexadecimal
		4.3.2 Using Hexadecimal to Represent Binary
	4.4 Calculating Number Sizes
		4.4.1 Calculating the Maximum Value of a Binary Number
		4.4.2 Calculating Memory Size
		4.4.3 Converting Between Bytes and Kilobytes
	4.5 Numbers in Assembly Programs
	4.6 Numbers in C Programs
	4.6 Summary
Chapter 5 • AVR Registers and Memory Map
	5.1 AVR Registers
		5.1.1 General Purpose Working Registers
		5.1.2 I/O Registers
	5.2 Using General Purpose Registers
		5.2.1 Adding Two Registers
		5.2.2 Incrementing a Register
	5.3 AVR Memory Map
		5.3.1 Program Memory
		5.3.2 Data Memory
		5.3.3 EEPROM
	5.4 Accessing SRAM in Assembler Programs
		5.4.1 SRAM Store and Load Example
		5.4.2 Store and Load Example in the Simulator
		5.4.3 SRAM Start Addresses
	5.5 Summary
Chapter 6 • AVR Internal Architecture
	6.1 Clock Pulses and Program Counter
		6.1.1 Clock Pulses
		6.1.2 Clock Pulse Period and Frequency
			6.1.2.1 ATtiny13(A) Default Clock Frequency
			6.1.2.2 ATtiny25/45/85 Default Clock Frequency
			6.1.2.3 RC Oscillator Accuracy
			6.1.2.4 Clock Sources and Improving Accuracy
			6.1.2.5 Calculating Clock Period from Frequency
			6.1.2.6 Calculating Clock Frequency from Period
		6.1.3 The Program Counter
	6.2 Microcontroller Buses
	6.3 Harvard and von Neumann Architectures
	6.4 Fetching and Executing Instructions
	6.5 Status Register
		6.5.1 Zero Flag
		6.5.2 Negative Flag
	6.6 Stack and Stack Pointer
		6.6.1 How the Stack Works
		6.6.2 Accessing the Stack with PUSH and POP
		6.6.3 Calling a Subroutine
	6.7 LED Blink Program Fully Explained
	6.8 AVR Instruction Encoding
	6.9 Addressing Modes
		6.9.1 Register Direct Addressing
		6.9.2 I/O Direct Addressing
		6.9.3 Other Addressing Modes
	6.10 Summary
Chapter 7 • Arithmetic and Logic Instructions
	7.1 Positive and Negative Numbers
		7.1.1 1’s Compliment Numbers
		7.1.2 2’s Compliment Numbers
	7.2 Addition
		7.2.1 ADD – Add without Carry
		7.2.2 ADC – Add with Carry
	7.3 Subtraction
	7.4 Logic Instructions
		7.4.1 Logical AND
		7.4.2 Logical OR
		7.4.3 Logical Exclusive OR
	7.5 Other Arithmetic and Logic Instructions
	7.6 Summary
Chapter 8 • Programming AVR I/O Ports
	8.1 Instructions for Accessing I/O Registers
		8.1.1 Reading and Writing I/O Registers with IN and OUT
			8.1.1.1 The IN Instruction
			8.1.1.2 The OUT Instruction
		8.1.2 I/O Register Bit Manipulation and Testing
		8.1.3 Accessing I/O Registers as Data Space
	8.2 I/O Ports
		8.2.1 Configuring I/O Pins as Outputs in Assembler
			8.2.1.1 Five LED 8-pin ATtiny Circuit
			8.2.1.2 Using debugWIRE or ISP/SPI to Program an ATtiny AVR
				Program-only Programmers
				Peripheral Hardware Devices Interfering with Programming
				Putting the AVR into debugWIRE Mode
			8.2.1.3 Build the 5 LED ATtiny Circuit on Breadboard
			8.2.1.4 Assembly Code for the 5 LED Count Circuit
			8.2.1.5 Select the Debugger or Simulator
			8.2.1.6 What the LED Count Assembler Code Does
			8.2.1.7 Build and Run the Program
			8.2.1.8 How the LED Count Assembler Program Works
			8.2.1.9 Using a Breakpoint in the Debugger
		8.2.2 Configuring I/O Pins as Outputs in C
			8.2.2.1 LED Count C Code
			8.2.2.2 How the LED Count C Code Works
			8.2.2.3 Running the LED Count C Code
			8.2.2.4 LED Count C Code Disassembly
		8.2.3 Limiting a Count Value
		8.2.4 Three Ways to Toggle an LED with an AVR
			8.2.4.1 Toggling an LED by Value
			8.2.4.2 Toggling an LED by Exclusive OR
			8.2.4.3 Toggling an LED with the PINB Register
		8.2.5 Configuring I/O Pins as Inputs
	8.3 Summary
Chapter 9 • Assembly Language Elements
	9.1 Instructions and Labels
	9.2 The Preprocessor and Include Files
	9.3 Assembler Directives
		9.3.1 Specifying Code and Data Locations
			9.3.1.1 ORG Assembler Directive
			9.3.1.2 CSEG Code Segment Directive
			9.3.1.3 DSEG Data Segment and BYTE Directives
			9.3.1.4 ESEG EEPROM Segment Directive
		9.3.2 Reserving Memory
			9.3.2.1 BYTE
			9.3.2.2 DB – Define Constant Byte
				Modified Harvard Architecture
				Example Code using the DB Assembler Directive
				CSEG Directive and First RJMP Instruction
				Usage of the DB Assembler Directive
				Data Formats and Null Terminating Strings
				Location of DB Data in Program Memory and Alignment
				16-bit Address Pointer Registers
				Loading the Z Register
				Reading Bytes from Program Memory
				Running the Example Code
			9.3.2.3 DW – Define Constant Word
			9.3.2.4 DD – Define Constant Double-word
			9.3.2.5 DQ – Define Constant Quad-word
		9.3.3 Defining Names for Registers with DEF
		9.3.4 Equating Names to Expressions using EQU and SET
		9.3.5 Conditional Assembly
	9.4 Other Assembly Language Elements
	9.5 Further Reading
	9.6 Summary
Chapter 10 • AVR Timing, Timers and Interrupts
	10.1 Instruction Timing
		10.1.1 AVR CPU Versions
		10.1.2 Instruction Timing Examples
			10.1.2.1 The NOP Instruction
			10.1.2.2 16-bit and 32-bit Instruction Timing
			10.1.2.3 Timing of Branch Instructions
				The Simulator Cycle Counter and Stop Watch
				Simulator Cycle Counter Bug
	10.2 Assembly Language Time Delay
		10.2.1 Calculating a Software Delay Subroutine Time Delay
			10.2.1.1 Delay Subroutine Cycle Counter Measurement
			10.2.1.2 Delay Subroutine Mathematical Formula
		10.2.2 A Better Software Delay Subroutine
			10.2.2.1 Principle of Operation
			10.2.2.2 32-bit Subtraction with 8-bit Registers
			10.2.2.3 Timing of the Code
			10.2.2.4 Testing the Code in Microchip Studio
		10.2.3 A Changeable Software Time Delay Subroutine
			10.2.3.1 Splitting an Assembly Language Project into Files
			10.2.3.2 How the wait_ms Subroutine Works
			10.2.3.3 Limits of the wait_ms Subroutine
				Simplifying the Formula
				Calculating the Maximum Delay Time of the Subroutine
				Posing Value Limits in Assembly Language
				Number Size Limits in the Assembler Program
				Solution to Flagging Out of Range Upper Values
				Flagging Out of Range High and Low Values
		10.2.4 Passing a Value to a Subroutine
			10.2.4.1 Simplest Way to Pass a Value
			10.2.4.2 Improved Way to Pass a Value
	10.3 Calling an Assembly Subroutine from C Code
		10.3.1 Passing a Value to an Assembly Subroutine from C
			10.3.1.1 Testing the wait_ms_c Project Code
			10.3.1.2 How the wait_ms_c Project Code Works
		10.3.2 Returning a Value from an Assembly Subroutine in C
	10.4 Polled Timer Delay
		10.4.1 Timer/Counter0 Registers
			10.4.1.1 Timer/Counter0 Register Addresses
			10.4.1.2 Using Counter/Timer0 as a Timer
		10.4.2 Polled Timer Assembly Program
			10.4.2.1 The IFNDEF Directive
			10.4.2.2 Left Shift Operator
			10.4.2.3 Register Write or Read-Modify-Write
			10.4.2.4 Initializing Timer 0
			10.4.2.5 Polling Timer 0
			10.4.2.6 Running the Code in the Simulator
		10.4.3 Polled Timer C Program
	10.5 Timer Interrupt Delay
		10.5.1 How Interrupts Work
		10.5.2 The Interrupt Vector Table
		10.5.3 Assembly Program Timer Interrupt
			10.5.3.1 ATtiny13(A) Timer Interrupt Project
				The Interrupt Vector Table
				Main Program Code
				Interrupt Service Routine Code
				Running the Timer Interrupt Code
			10.5.3.2 ATtiny25/45/85 Timer Interrupt Project
			10.5.3.3 Universal Timer Interrupt Project
		10.5.4 C Program Timer Interrupt
	10.6 Summary
Chapter 11 • The AVR Instruction Set
	11.1 AVR Instruction Set Overview and Categories
	11.2 A Guided Tour through the ATtiny AVR Instruction Set
		11.2.1 Arithmetic and Logic Instructions
			11.2.1.1 Add and Subtract Instructions
				Addition Instructions
				Subtraction Instructions
			11.2.1.2 Logical Instructions
				Logical AND
				Logical OR
				Logical Exclusive OR
			11.2.1.3 Increment and Decrement Instructions
			11.2.1.4 Sign Change Instructions
			11.2.1.5 Bit Set and Clear Instructions
			11.2.1.6 Register Set, Clear and Test Instructions
		11.2.2 Branch Instructions
			11.2.2.1 Jump Instructions
			11.2.2.2 Subroutine Call Instructions
			11.2.2.3 Return from Subroutine and Interrupt Instructions
			11.2.2.4 Compare Instructions
			11.2.2.5 Skip Instructions
			11.2.2.6 Branch Instructions
				Branch if Bit in SREG Set or Cleared
				Branch if Equal or Not Equal – SREG Z Flag
				Branch if Carry Set or Cleared – SREG C Flag
				Branch if Same or Higher, or Lower – SREG C Flag
				Branch if Minus or Plus – SREG N Flag
				Branch if Greater or Equal, or Less Than Signed – SREG S Flag
				Branch if Half Carry Flag Set or Cleared – SREG H Flag
				Branch if T Bit Set or Cleared – SREG T Flag
				Branch if Overflow Flag Set or Cleared – SREG V Flag
				Branch if Interrupt Enabled or Disabled – SREG I Flag
		11.2.3 Bit and Bit-test Instructions
			11.2.3.1 Bit Set and Clear Instructions
			11.2.3.2 Shift, Rotate and Swap Instructions
				Logical Shift Instructions
				Rotate through Carry Instructions
				Logical Shift and Rotate Code Example
				Led Chaser Logical Shift Code Example
				Arithmetic Shift and Swap Instructions
			11.2.3.3 Status Register Bit Set and Clear Instructions
				Set or Clear SREG Bit
				Store or Load SREG T Bit to/from Register
				Set or Clear Carry Flag – SREG C Bit
				Set or Clear Negative Flag – SREG N Bit
				Set or Clear Zero Flag – SREG Z Bit
				Set or Clear Global Interrupt Flag Bit – SREG I Bit
				Set or Clear Sign Flag – SREG S Bit
				Set or Clear Two’s Compliment Overflow Flag – SREG V Bit
				Set or Clear T Bit in SREG – SREG T Bit
				Set and Clear Half Carry Flag – SREG H bit
		11.2.4 Data Transfer Instructions
			11.2.4.1 Move/Copy Instructions
			11.2.4.2 Load Immediate Instruction
			11.2.4.3 Load Indirect Instructions
			11.2.4.4 Store Indirect Instructions
			11.2.4.5 Load Indirect with Displacement
			11.2.4.6 Store Indirect with Displacement
			11.2.4.7 Load Direct from SRAM
			11.2.4.8 Store Direct to SRAM
			11.2.4.9 Load Program Memory Instructions
			11.2.4.10 Store Program Memory
			11.2.4.11 Port IN and OUT Instructions
			11.2.4.12 PUSH and POP Instructions
		11.2.5 MCU Control Instructions
	11.3 Entire AVR Instruction Set
		11.3.1 Number of AVR Instructions
			11.3.1.1 Total Number of AVR Instructions
			11.3.1.2 Number of ATtiny AVR Instructions
			11.3.1.3 Discrepancies in Documentation
		11.3.2 Other AVR Instructions
			11.3.2.1 Arithmetic and Logic Instructions
			11.3.2.2 Branch Instructions
			11.3.2.3 Data Transfer Instructions
		11.3.3 Putting Instructions into Perspective
			11.3.3.1 The Full AVR Instruction Set
			11.3.3.2 The Plain AVR CPU
			11.3.3.3 Reduced AVRrc Core
			11.3.3.4 AVRe and AVRxt Cores
			11.3.3.5 AVRe+ CPU
			11.3.3.6 AVRxm CPU
Chapter 12 • Software Tools and Settings
	12.1 AVR Assembler Programs
		12.1.1 The AVRASM2 Assembler
			12.1.1.1 Building a Project with AVRASM2
			12.1.1.2 AVRASM2 on the Command Line
			12.1.1.3 AVRASM2 Options in Microchip Studio
			12.1.1.4 List File Options
		12.1.2 The AVR-AS Assembler
		12.1.3 The AVRA Assembler
	12.2 The GNU C Toolchain
	12.3 Where to from Here?
		12.3.1 Objectives Achieved
		12.3.2 What was Not Covered
		12.3.3 Other AVR Microcontrollers
		12.3.4 Assembly Language Resources
Appendix A • External Programmer Setup
	A.1 Hobby USB Programmer Capabilities
		A.1.1 Differences Between Hobby Programmers and the Atmel-ICE
		A.1.2 Programming Interfaces
		A.1.3 Using Hobby USB Programmers with this Book
	A.2 Overview of External Programmer Setup
	A.3 External Programmer Setup
		A.3.1 Install a Driver
			A.3.1.1 USBasp Driver
			A.3.1.2 USBtinyISP Driver
			A.3.1.3 Arduino Uno Sketch
		A.3.2 Download and Install avrdude
		A.3.3 Build an AVR Circuit and Connect a Programmer
			A.3.3.1 Connecting a USBasp
				10-pin Male Header
				10-pin Female Connector on Ribbon Cable
				6-pin Adapter (ISP/SPI)
			A.3.3.2 Connecting a USBtinyISP
				6-pin Male Header
				6-pin Female Connector on Ribbon Cable
			A.3.3.3 Connecting an Arduino Uno ArduinoISP
		A.3.4 Programming Parameters
			A.3.4.1 Documentation for avrdude
			A.3.4.2 Parameters for avrdude Explained
			A.3.4.3 Parameters for a USBasp
			A.3.4.4 Parameters for a USBtinyISP
			A.3.4.5 Parameters for an ArduinoISP
		A.3.5 Microchip Studio External Tool Setup
			A.3.5.1 Open an Assembly or C Project
			A.3.5.2 Add an External Tool in Microchip Studio
				USBasp
				USBtinyISP
				ArduinoISP (Arduino Uno with ArduinoISP sketch loaded)
			A.3.5.3 Add a Toolbar Button for the External Tool
		A.3.6 Testing the Programmer
		A.3.7 Programming Problems and Solutions
Appendix B • Alternate Circuits and Programs
	B.1 8-Pin PDIP ATtiny13/25/45/85
	B.2 14-Pin PDIP ATtiny24/44/84
	B.3 20-Pin PDIP ATtiny26/261/461/861 and ATtiny2313/4313
	B.4 28-Pin PDIP ATtiny48/88
	B.5 Alternate Programs
		B.5.1 Alternate LED Blink Assembly Program
		B.5.2 Alternate LED Blink C Program
Appendix C • The ASCII Table
	C.1 Printable Characters
	C.2 ASCII Table
Index