AT90USB64/128
29.2.1
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.
29.3 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.
AT90USB64/128 Signature Bytes:
1. 0x000: 0x1E (indicates manufactured by Atmel).
2. 0x001: 0x97 (indicates 128KB Flash memory).
3. 0x002: 0x82 (indicates AT90USBxxxdevice).
29.4 Calibration Byte
The AT90USB64/128 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.
29.5 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 AT90USB64/128. Pulses are assumed to
be at least 250 ns unless otherwise noted.
29.5.1
Signal Names
In this section, some pins of the AT90USB64/128 are referenced by signal names describing
their functionality during parallel programming, see Figure 29-1 and Table 29-6. 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 29-9.
When pulsing WR or OE, the command loaded determines the action executed. The different
commands are shown in Table 29-10.
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7593A–AVR–02/06
ATMEL [ ATMEL ]
