26.2.1
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.
26.3 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 ATmega169P the signature bytes are:
1. 0x000: 0x1E (indicates manufactured by Atmel).
2. 0x001: 0x94 (indicates 16KB Flash memory).
3. 0x002: 0x05 (indicates ATmega169P device when 0x001 is 0x94).
26.4 Calibration Byte
The ATmega169P 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 auto-
matically written into the OSCCAL Register to ensure correct frequency of the calibrated RC
Oscillator.
26.5 Page Size
Table 26-6. No. of Words in a Page and No. of Pages in the Flash
Flash Size
Page Size
PCWORD
No. of Pages
PCPAGE
PCMSB
8K words (16K bytes)
64 words
PC[5:0]
128
PC[12:6]
12
Table 26-7. No. of Words in a Page and No. of Pages in the EEPROM
EEPROM Size
Page Size
PCWORD
No. of Pages
PCPAGE
EEAMSB
512 bytes
4 bytes
EEA[1:0]
128
EEA[8:2]
8
26.6 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 ATmega169P. Pulses are assumed to be
at least 250 ns unless otherwise noted.
26.6.1
Signal Names
In this section, some pins of the ATmega169P are referenced by signal names describing their
functionality during parallel programming, see Figure 26-1 and Table 26-8. 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 positive pulse.
The bit coding is shown in Table 26-10.
298
ATmega169P
8018A–AVR–03/06
ATMEL [ ATMEL ]
