Copyright
©
Kanda 2013
5
AVR microcontroller default fuses
New AVR devices come with the Clock Source set to RC Internal Oscillator by default.
The actual speed of the oscillator varies from 0.5MHz to 4MHz depending on the device.
This means that programs will run slower than expected, because the
AVR is NOT
running from the 8MHz clock on the STK200 board.
To change the Clock source
,
go to Fuses and Lockbits tab and change CLKSEL fuses
from Internal Oscillator to External Crystal/Resonator 3 – 8MHz (1110, 1111). Then go to
Device menu > Program > Fuses.
Other features of AVRISP
Auto Program
It can get a bit tedious carrying out all these steps individually, especially if you want to
check that the code has loaded properly (Verify) and program the EEPROM as well. This
is where Device > Auto Program (F5 key) is useful.
To use Auto Program feature, first go to Device > Auto Program Options and set the
operations you want to carry out. Now selecting Device > Auto Program or pressing F5
will carry out all these operations.
Fuses and Lockbits
Click on the Fuses and Lockbits Tab to view the Fuse screen. These are settings on the
Atmega128 that can be altered to affect the way the device runs and interacts with the
circuit.
The default fuses will work happily on the STK300 board, but you may want to alter them
to make the clock run from the 8MHz crystal on the board. Leave
JTAGEN
checked to
use emulator. Full descriptions of each fuse and what they do are in the device
datasheet – see Documentation > AVR Datasheets folder on CD for the datasheet on
Atmega128.
On the right of the Fuse screen is a second tab marked Lockbits and Boot Options. This
screen displays the various security settings and block options available. Again, these
are described in the Atmega128 datasheet.
Status
The Status Tab lists the operations that have been carried out during the current
programming session.
Serial Numbers
Serial numbers can be added to the Code space (Flash) or Data Memory (EEPROM) in
a variety of formats. If Auto Program is used, the serial number will increment with every
Auto-program cycle.
View Menu
CRC Checksums
This gives the checksum calculations in different formats for the whole buffer or just the
used buffer. Applies to both Flash and EEPROM
