User guide
Table Of Contents
- Features
- Pin Configurations
- Overview
- AVR CPU Core
- AVR ATmega162 Memories
- System Clock and Clock Options
- Power Management and Sleep Modes
- System Control and Reset
- Interrupts
- I/O-Ports
- Introduction
- Ports as General Digital I/O
- Alternate Port Functions
- Register Description for I/O-Ports
- Port A Data Register – PORTA
- Port A Data Direction Register – DDRA
- Port A Input Pins Address – PINA
- Port B Data Register – PORTB
- Port B Data Direction Register – DDRB
- Port B Input Pins Address – PINB
- Port C Data Register – PORTC
- Port C Data Direction Register – DDRC
- Port C Input Pins Address – PINC
- Port D Data Register – PORTD
- Port D Data Direction Register – DDRD
- Port D Input Pins Address – PIND
- Port E Data Register – PORTE
- Port E Data Direction Register – DDRE
- Port E Input Pins Address – PINE
- External Interrupts
- 8-bit Timer/Counter0 with PWM
- Timer/Counter0, Timer/Counter1, and Timer/Counter3 Prescalers
- 16-bit Timer/Counter (Timer/Counter1 and Timer/Counter3)
- Restriction in ATmega161 Compatibility Mode
- Overview
- Accessing 16-bit Registers
- Timer/Counter Clock Sources
- Counter Unit
- Input Capture Unit
- Output Compare Units
- Compare Match Output Unit
- Modes of Operation
- Timer/Counter Timing Diagrams
- 16-bit Timer/Counter Register Description
- Timer/Counter1 Control Register A – TCCR1A
- Timer/Counter3 Control Register A – TCCR3A
- Timer/Counter1 Control Register B – TCCR1B
- Timer/Counter3 Control Register B – TCCR3B
- Timer/Counter1 – TCNT1H and TCNT1L
- Timer/Counter3 – TCNT3H and TCNT3L
- Output Compare Register 1 A – OCR1AH and OCR1AL
- Output Compare Register 1 B – OCR1BH and OCR1BL
- Output Compare Register 3 A – OCR3AH and OCR3AL
- Output Compare Register 3 B – OCR3BH and OCR3BL
- Input Capture Register 1 – ICR1H and ICR1L
- Input Capture Register 3 – ICR3H and ICR3L
- Timer/Counter Interrupt Mask Register – TIMSK(1)
- Extended Timer/Counter Interrupt Mask Register – ETIMSK(1)
- Timer/Counter Interrupt Flag Register – TIFR(1)
- Extended Timer/Counter Interrupt Flag Register – ETIFR(1)
- 8-bit Timer/Counter2 with PWM and Asynchronous operation
- Serial Peripheral Interface – SPI
- USART
- Analog Comparator
- JTAG Interface and On-chip Debug System
- IEEE 1149.1 (JTAG) Boundary-scan
- Boot Loader Support – Read-While-Write Self-programming
- Features
- Application and Boot Loader Flash Sections
- Read-While-Write and No Read-While-Write Flash Sections
- Boot Loader Lock Bits
- Entering the Boot Loader Program
- Addressing the Flash During Self- programming
- Self-programming the Flash
- Performing Page Erase by SPM
- Filling the Temporary Buffer (Page Loading)
- Performing a Page Write
- Using the SPM Interrupt
- Consideration while Updating BLS
- Prevent Reading the RWW Section During Self- programming
- Setting the Boot Loader Lock Bits by SPM
- EEPROM Write Prevents Writing to SPMCR
- Reading the Fuse and Lock Bits from Software
- Preventing Flash Corruption
- Programming Time for Flash When Using SPM
- Simple Assembly Code Example for a Boot Loader
- ATmega162 Boot Loader Parameters
- Memory Programming
- Program And Data Memory Lock Bits
- Fuse Bits
- Signature Bytes
- Calibration Byte
- Parallel Programming Parameters, Pin Mapping, and Commands
- Parallel Programming
- Enter Programming Mode
- Considerations for Efficient Programming
- Chip Erase
- Programming the Flash
- Programming the EEPROM
- Reading the Flash
- Reading the EEPROM
- Programming the Fuse Low Bits
- Programming the Fuse High Bits
- Programming the Extended Fuse Bits
- Programming the Lock Bits
- Reading the Fuse and Lock Bits
- Reading the Signature Bytes
- Reading the Calibration Byte
- Parallel Programming Characteristics
- Serial Downloading
- SPI Serial Programming Pin Mapping
- Programming via the JTAG Interface
- Programming Specific JTAG Instructions
- AVR_RESET (0xC)
- PROG_ENABLE (0x4)
- PROG_COMMANDS (0x5)
- PROG_PAGELOAD (0x6)
- PROG_PAGEREAD (0x7)
- Data Registers
- Reset Register
- Programming Enable Register
- Programming Command Register
- Virtual Flash Page Load Register
- Virtual Flash Page Read Register
- Programming Algorithm
- Entering Programming Mode
- Leaving Programming Mode
- Performing Chip Erase
- Programming the Flash
- Reading the Flash
- Programming the EEPROM
- Reading the EEPROM
- Programming the Fuses
- Programming the Lock Bits
- Reading the Fuses and Lock Bits
- Reading the Signature Bytes
- Reading the Calibration Byte
- Electrical Characteristics
- ATmega162 Typical Characteristics
- Active Supply Current
- Idle Supply Current
- Power-down Supply Current
- Power-save Supply Current
- Standby Supply Current
- Pin Pull-up
- Pin Driver Strength
- Pin Thresholds and Hysteresis
- BOD Thresholds and Analog Comparator Offset
- Internal Oscillator Speed
- Current Consumption of Peripheral Units
- Current Consumption in Reset and Reset Pulsewidth
- Register Summary
- Instruction Set Summary
- Ordering Information
- Packaging Information
- Erratas
- Datasheet Change Log for ATmega162
- Table of Contents

217
ATmega162/V
2513E–AVR–09/03
Note that the user software can never read any code that is located inside the RWW
section during a Boot Loader software operation. The syntax “Read-While-Write sec-
tion” refers to which section that is being programmed (erased or written), not which
section that actually is being read during a Boot Loader software update.
RWW – Read-While-Write
Section
If a Boot Loader software update is programming a page inside the RWW section, it is
possible to read code from the Flash, but only code that is located in the NRWW sec-
tion. During an ongoing programming, the software must ensure that the RWW section
never is being read. If the user software is trying to read code that is located inside the
RWW section (i.e., by a call/jmp/lpm or an interrupt) during programming, the software
might end up in an unknown state. To avoid this, the interrupts should either be disabled
or moved to the Boot Loader section. The Boot Loader section is always located in the
NRWW section. The RWW Section Busy bit (RWWSB) in the Store Program Memory
Control Register (SPMCR) will be read as logical one as long as the RWW section is
blocked for reading. After a programming is completed, the RWWSB must be cleared by
software before reading code located in the RWW section. See “Store Program Memory
Control Register – SPMCR” on page 220. for details on how to clear RWWSB.
NRWW – No Read-While-Write
Section
The code located in the NRWW section can be read when the Boot Loader software is
updating a page in the RWW section. When the Boot Loader code updates the NRWW
section, the CPU is halted during the entire Page Erase or Page Write operation.
Figure 93. Read-While-Write vs. No Read-While-Write
Table 89. Read-While-Write Features
Which Section does the Z-
pointer Address During the
Programming?
Which Section Can be
Read During
Programming?
Is the CPU
Halted?
Read-While-
Write
Supported?
RWW section NRWW section No Yes
NRWW section None Yes No
Read-While-Write
(RWW) Section
No Read-While-Write
(NRWW) Section
Z-pointer
Addresses RWW
Section
Z-pointer
Addresses NRWW
Section
CPU is Halted
During the Operation
Code Located in
NRWW Section
Can be Read During
the Operation