E.3 Modern AVR Parts

Modern 8-bit AVR devices have the following memories in addition to eeprom, flash, signature and lock:

fuse0

A.k.a. wdtcfg: watchdog configuration

fuse1

A.k.a. bodcfg: brownout detection configuration

fuse2

A.k.a. osccfg: oscillator configuration

fuse4

A.k.a. tcd0cfg (not all devices): timer counter type D configuration

fuse5

A.k.a. syscfg0: system configuration 0

fuse6

A.k.a. syscfg1: system configuration 1

fuse7

A.k.a. append or codesize: either the end of the application code section or the code size in blocks of 256/512 bytes

fuse8

A.k.a. bootend or bootsize: end of the boot section or the boot size in blocks of 256/512 bytes

fusea

A.k.a. pdicfg: configures/locks updi access; it is the only fuse that consists of two bytes

fuses

A logical memory of up to 16 bytes containing all fuseX of a part, which can be used to program all fuses at the same time

osc16err

Two bytes typically describing the 16 MHz oscillator frequency error at 3 V and 5 V, respectively

osc20err

Two bytes typically describing the 20 MHz oscillator frequency error at 3 V and 5 V, respectively

osccal16

Two oscillator calibration bytes for 16 MHz

osccal20

Two oscillator calibration bytes for 20 MHz

prodsig

Read-only memory section for factory programmed data such as the signature, calibration values and serial number

sigrow

Memory alias for prodsig

sernum

Serial number with a unique ID for the part (10 or 16 bytes)

tempsense

Temperature sensor calibration values

bootrow

Extra page of memory that is only accessible by the MCU in bootloader code; UDPI can read and write this memory only when the device is unlocked

userrow

Extra page of EEPROM memory that can be used for firmware settings; this memory is not erased during a chip erase

sib

Special system information block memory with information about AVR family, chip revision etc.

io

Volatile register memory; AVRDUDE can program this memory but this is of limited utility because anything written to the io memory will be undefined or lost after reset; writing to individual registers in the terminal can still be used, e.g., to test I/O ports

sram

Volatile RAM memory; can be read and written but contents will be lost after reset

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