AT90USB646 datasheet(369/459 Pages) ATMEL

369 / 459 page

369

7593H–AVR–11/08

ATmega32U6/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.

AT90USB128x Signature Bytes:

0x000: 0x1E (indicates manufactured by Atmel).

0x001: 0x97 (indicates 128KB Flash memory).

0x002: 0x82 (indicates AT90USB128x device).

AT90USB64x Signature Bytes:

0x000: 0x1E (indicates manufactured by Atmel).

0x001: 0x96 (indicates 64KB Flash memory).

0x002: 0x82 (indicates AT90USB64x device).

ATMega32U6 Signature Bytes:

0x000: 0x1E (indicates manufactured by Atmel).

0x001: 0x95 (indicates 32KB Flash memory).

0x002: 0x88 (indicates ATMega32U6 device).

29.4

Calibration Byte

The ATmega32U6/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 ATmega32U6/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 ATmega32U6/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.

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