AT90USB647-MU Atmel, AT90USB647-MU Datasheet - Page 361

• Manufacturer Part Number: AT90USB647-MU
• Description: MCU, 8BIT, 64K FLASH, USB, 64QFN
• Manufacturer: Atmel

Specifications of AT90USB647-MU

• Controller Family/series: AT90
• No. Of I/o's: 48
• Eeprom Memory Size: 2KB
• Ram Memory Size: 4KB
• Cpu Speed: 16MHz
• No. Of: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 64KB
• Oscillator Type: External, Internal
• Package: 64QFN EP
• Device Core: AVR
• Family Name: AT90
• Maximum Speed: 20 MHz
• Ram Size: 4 KB
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 48
• Interface Type: SPI/TWI/USART/USB
• On-chip Adc: 8-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 4
• Lead Free Status / Rohs Status: Details

28.7.11
28.7.12
7593K–AVR–11/09
Preventing Flash Corruption
Programming Time for Flash when Using SPM
AT90USB64/128 includes a unique 10 bytes serial number located in the signature row. This
unique serial number can be used as a USB serial number in the device enumeration process.
The pointer addresses to access this unique serial number are given in
361..
Table 28-6.
Note:
During periods of low V
too low for the CPU and the Flash to operate properly. These issues are the same as for board
level systems using the Flash, and the same design solutions should be applied.
A Flash program corruption can be caused by two situations when the voltage is too low. First, a
regular write sequence to the Flash requires a minimum voltage to operate correctly. Secondly,
the CPU itself can execute instructions incorrectly, if the supply voltage for executing instructions
is too low.
Flash corruption can easily be avoided by following these design recommendations (one is
sufficient):
The calibrated RC Oscillator is used to time Flash accesses.
gramming time for Flash accesses from the CPU.
Table 28-7.
Signature Byte
Device Signature Byte 1
Device Signature Byte 2
Device Signature Byte 3
RC Oscillator Calibration Byte
Unique Serial Number
Flash write (Page Erase, Page Write,
and write Lock bits by SPM)
1. If there is no need for a Boot Loader update in the system, program the Boot Loader
2. Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
3. Keep the AVR core in Power-down sleep mode during periods of low V
Lock bits to prevent any Boot Loader software updates.
This can be done by enabling the internal Brown-out Detector (BOD) if the operating
voltage matches the detection level. If not, an external low V
can be used. If a reset occurs while a write operation is in progress, the write operation
will be completed provided that the power supply voltage is sufficient.
vent the CPU from attempting to decode and execute instructions, effectively protecting
the SPMCSR Register and thus the Flash from unintentional writes.
All other addresses are reserved for future use.
Signature Row Addressing
SPM Programming Time
Symbol
CC
, the Flash program can be corrupted because the supply voltage is
Min Programming Time
Z-Pointer Address
0x0000
0x0002
0x0004
0x0001
From 0x000E to 0x0018
3.7 ms
Table 28-7
Max Programming Time
AT90USB64/128
CC
reset protection circuit
4.5 ms
shows the typical pro-
Table 28-6 on page
CC
. This will pre-
361