287
2593O–AVR–02/12
ATmega644
25.2.1
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.
25.3
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. The ATmega644 signature bytes are given in
Table25.4
Calibration Byte
The ATmega644 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 auto-
matically written into the OSCCAL Register to ensure correct frequency of the calibrated RC
Oscillator.
25.5
Page Size
25.6
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 ATmega644. Pulses are assumed to be at
least 250 ns unless otherwise noted.
25.6.1
Signal Names
In this section, some pins of the ATmega644 are referenced by signal names describing their
the following table are referenced by pin names.
Table 25-6.
Device and JTAG ID
Part
Signature Bytes Address
JTAG
0x000
0x001
0x002
Part Number
Manufacture ID
ATmega644
0x1E
0x96
0x09
9609
0x1F
Table 25-7.
No. of Words in a Page and No. of Pages in the Flash
Device
Flash Size
Page Size
PCWORD
No. of Pages
PCPAGE
PCMSB
ATmega644
32K words (64 Kbytes)
128 words
PC[6:0]
256
PC[14:7]
14
Table 25-8.
No. of Words in a Page and No. of Pages in the EEPROM
Device
EEPROM Size
Page Size
PCWORD
No. of Pages
PCPAGE
EEAMSB
ATmega644
2 Kbytes
8 bytes
EEA[2:0]
256
EEA[10:3]
10