296
2552K–AVR–04/11
ATmega329/3290/649/6490
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if
Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.
27.2.1
Latching of Fuses
The fuse values are latched when the device enters programming mode and changes of the
fuse values will have no effect until the part leaves Programming mode. This does not apply to
the EESAVE Fuse which will take effect once it is programmed. The fuses are also latched on
Power-up in Normal mode.
27.3
Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This
code can be read in both serial and parallel mode, also when the device is locked. The three
bytes reside in a separate address space.
For the ATmega329/3290/649/6490 the signature bytes are:
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
3.
27.4
Calibration Byte
The ATmega329/3290/649/6490 has a byte calibration value for the internal RC Oscillator. This
byte resides in the high byte of address 0x000 in the signature address space. During reset, this
byte is automatically written into the OSCCAL Register to ensure correct frequency of the cali-
brated RC Oscillator.
27.5
Parallel Programming Parameters, Pin Mapping, and Commands
This section describes how to parallel program and verify Flash Program memory, EEPROM
Data memory, Memory Lock bits, and Fuse bits in the ATmega329/3290/649/6490. Pulses are
assumed to be at least 250ns unless otherwise noted.
27.5.1
Signal Names
In this section, some pins of the ATmega329/3290/649/6490 are referenced by signal names
not described in the following table are referenced by pin names.
The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse.
When pulsing WR or OE, the command loaded determines the action executed. The different