Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 298
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 AVR 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 ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P the signature bytes are given in Table 27-
6.
27.4 Calibration byte
The ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P 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.
27.5 Page Size
Table 27-6. Device and JTAG ID
Part
Signature bytes address JTAG
0x000 0x001 0x002 Part number Manufacture ID
ATmega164A 0x1E 0x94 0x0F 940A 0x1F
ATmega164PA 0x1E 0x94 0x0A 940A 0x1F
ATmega324A 0x1E 0x95 0x15 9511 0x1F
ATmega324PA 0x1E 0x95 0x11 9511 0x1F
ATmega644A 0x1E 0x96 0x09 960A 0x1F
ATmega644PA 0x1E 0x96 0x0A 960A 0x1F
ATmega1284 0x1E 0x97 0x06 9705 0x1F
ATmega1284P 0x1E 0x97 0x05 9705 0x1F
Table 27-7. Number of words in a page and number of pages in the flash
Device Flash size Page size PCWORD No. of pages PCPAGE PCMSB
ATmega164A/ATmega164PA 8K words (16KBytes) 64 words PC[5:0] 128 PC[12:6] 12
ATmega324A/ATmega324PA 16K words (32KBytes) 64 words PC[5:0] 256 PC[13:6] 13
ATmega644A/ATmega644PA 32K words (64KBytes) 128 words PC[6:0] 256 PC[14:7] 14
ATmega1284/ATmega1284P 64K words (128KBytes) 128 words PC[6:0] 512 PC[15:7] 15