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7530J–AVR–03/12
Atmel ATmega48/88/168 Automotive
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.
25.3.1
ATmega48 Signature Bytes
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x92 (indicates 4KB Flash memory).
3.
0x002: 0x05 (indicates ATmega48 device when 0x001 is 0x92).
25.3.2
ATmega88 Signature Bytes
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x93 (indicates 8KB Flash memory).
3.
0x002: 0x0A (indicates ATmega88 device when 0x001 is 0x93).
25.3.3
ATmega168 Signature Bytes
1.
0x000: 0x1E (indicates manufactured by Atmel).
2.
0x001: 0x94 (indicates 16KB Flash memory).
3.
0x002: 0x06 (indicates ATmega168 device when 0x001 is 0x94).
25.4
Calibration Byte
The ATmega48/88/168 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.
25.5
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 ATmega48/88/168. Pulses are assumed
to be at least 250 ns unless otherwise noted.
25.5.1
Signal Names
In this section, some pins of the ATmega48/88/168 are referenced by signal names describing
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 positive pulse.
When pulsing WR or OE, the command loaded determines the action executed. The different