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Atmel AVR simulator written in x86 assembly
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README.md
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README.md

fastavr

Developing AVR code usually involves a lot of simulation, by using programs such as:

fastavr is like these, but with the main design goals of raw speed and simplicity of use.

Features

  • Supports all common AVR instructions (see below)
  • Optional user-definable behaviour of all AVR I/O ports
  • Interrupts and single-stepping
  • Possibility of simulating components using multi-threading
  • Much faster than a physical AVR

Example

See the file tester.c; this reads an AVR program (in IHEX8 format) and executes it on a emulated Atmega2560, causing bytes written to USART0 to be written to the console. It also defines a watchdog timer that can be used to auto-reset/kill a program that is in a run-away condition (as described in Atmel's datasheets). Also emulated are the programmable timers TIMER0 and TIMER1, as well as EEPROM memory (for handling non-volatile data).

Building

To build this project, you will need to have support for developing 32-bit programs installed. E.g. by installing libc6-dev-i386 on Debian.

Once you have that, this is likely to work:

make

Configuration options are found in avr_core_x86.s.

A quick test can be performed by running make selftest.

Todo/Limitations

  • The S flag is always stuck at V⊕O due to the way fastavr handles the flags. This should only be noticeable when using SES/SEV/SEO/CLS/CLV/CLO or writing SREG via I/O-space

  • SPM and DES instructions are supported as hooks for C functions; see the des-support branch for a AVR-compatible emulation of the DES instruction.

  • No support for Reduced Core AVR; cycle count not correct for XMEGA microcontrollers.

  • Not all illegal opcodes will result in an error. Neither will out-of-bounds SRAM accesses.

  • The core has not yet been ported to x86-64.

Acknowledgements

Writing this pet project couldn't have been possible without Michel Pollet's excellent simavr.

Without the μNaCl project, testing this simulator wouldn't have been possible as well: http://munacl.cryptojedi.org/atmega.shtml

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