Datasheet

338
2549O–AVR–05/12
ATmega640/1280/1281/2560/2561
30.2.1 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.
30.3 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 ATmega640/1280/1281/2560/2561 the signa-
ture bytes are given in Table 30-6.
30.4 Calibration Byte
The ATmega640/1280/1281/2560/2561 has a byte calibration value for the internal RC Oscilla-
tor. 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 calibrated RC Oscillator.
30.5 Page Size
30.6 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 ATmega640/1280/1281/2560/2561.
Pulses are assumed to be at least 250ns unless otherwise noted.
Table 30-6. Device and JTAG ID
Part
Signature Bytes Address JTAG
0x000 0x001 0x002 Part Number Manufacture ID
ATmega640 0x1E 0x96 0x08 9608 0x1F
ATmega1280 0x1E 0x97 0x03 9703 0x1F
ATmega1281 0x1E 0x97 0x04 9704 0x1F
ATmega2560 0x1E 0x98 0x01 9801 0x1F
ATmega2561 0x1E 0x98 0x02 9802 0x1F
Table 30-7. No. of Words in a Page and No. of Pages in the Flash
Flash Size Page Size PCWORD
No. of
Pages PCPAGE PCMSB
128K words (256Kbytes) 128 words PC[6:0] 1024 PC[16:7] 16
Table 30-8. No. of Words in a Page and No. of Pages in the EEPROM
EEPROM Size Page Size PCWORD
No. of
Pages PCPAGE EEAMSB
4Kbytes 8 bytes EEA[2:0] 512 EEA[11:3] 11