Datasheet
345
ATmega640/1280/1281/2560/2561
2549K–AVR–01/07
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.
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 signature bytes are given in Table 154.
Calibration Byte The ATmega640/1280/1281/2560/2561 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 calibrated RC Oscillator.
Page Size
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 250 ns unless
otherwise noted.
Signal Names In this section, some pins of the ATmega640/1280/1281/2560/2561 are referenced by
signal names describing their functionality during parallel programming, see Figure 138
and Table 157. Pins 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 posi-
tive pulse. The bit coding is shown in Table 160.
Table 154. 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 155. 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 (256K bytes) 128 words PC[6:0] 1024 PC[16:7] 16
Table 156. No. of Words in a Page and No. of Pages in the EEPROM
EEPROM Size Page Size PCWORD
No. of
Pages PCPAGE EEAMSB
4K bytes 8 bytes EEA[2:0] 512 EEA[11:3] 11