Datasheet

296
8011O–AVR–07/10
ATmega164P/324P/644P
24.2.1 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.
24.3 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 ATmega164P/324P/644P the signature bytes
are given in Table 24-6.
24.4 Calibration Byte
The ATmega164P/324P/644P 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.
24.5 Page Size
Table 24-6. Device and JTAG ID
Part
Signature Bytes Address JTAG
0x000 0x001 0x002 Part Number Manufacture ID
ATmega164P 0x1E 0x94 0x0A 940A 0x1F
ATmega324P 0x1E 0x95 0x08 9508 0x1F
ATmega644P 0x1E 0x96 0x0A 960A 0x1F
Table 24-7. No. of Words in a Page and No. of Pages in the Flash
Device Flash Size Page Size PCWORD No. of Pages PCPAGE PCMSB
ATmega164P 8K words (16 Kbytes) 64 words PC[5:0] 128 PC[12:6] 12
ATmega324P 16K words (32 Kbytes) 64 words PC[5:0] 256 PC[13:6] 13
ATmega644P 32K words (64 Kbytes) 128 words PC[6:0] 256 PC[14:7] 14
Table 24-8. No. of Words in a Page and No. of Pages in the EEPROM
Device EEPROM Size Page Size PCWORD No. of Pages PCPAGE EEAMSB
ATmega164P 512 bytes 4 bytes EEA[1:0] 128 EEA[8:2] 8
ATmega324P 1 Kbytes 4 bytes EEA[1:0] 256 EEA[9:2] 9
ATmega644P 2 Kbytes 8 bytes EEA[2:0] 256 EEA[10:3] 10