ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 288

• Manufacturer Part Number: ATMEGA644P-A15MZ
• Description: MCU AVR 64KB FLASH 16MHZ 44QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-A15MZ

• Package / Case: 44-VQFN Exposed Pad
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Speed: 16MHz
• Number Of I /o: 32
• Eeprom Size: 2K x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 4K x 8
• Program Memory Size: 64KB (64K x 8)
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: I²C, SPI, UART/USART
• Core Size: 8-Bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

24.8.10
24.8.11
288
ATmega164P/324P/644P
Reading the Signature Row from Software
Preventing Flash Corruption
To read the Signature Row from software, load the Z-pointer with the signature byte address
given in
LPM instruction is executed within three CPU cycles after the SIGRD and SPMEN bits are set in
SPMCSR, the signature byte value will be loaded in the destination register. The SIGRD and
SPMEN bits will auto-clear upon completion of reading the Signature Row Lock bits or if no LPM
instruction is executed within three CPU cycles. When SIGRD and SPMEN are cleared, LPM will
work as described in the Instruction set Manual.
Table 24-5.
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):
1. If there is no need for a Boot Loader update in the system, program the Boot Loader Lock
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
Signature Byte
Device Signature Byte 1
Device Signature Byte 2
Device Signature Byte 3
RC Oscillator Calibration Byte
bits to prevent any Boot Loader software updates.
This can be done by enabling the internal Brown-out Detector (BOD) if the operating volt-
age matches the detection level. If not, an external low V
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.
Table 24-5 on page 288
Signature Row Addressing
CC
, the Flash program can be corrupted because the supply voltage is
and set the SIGRD and SPMEN bits in SPMCSR. When an
Z-Pointer Address
0x0000
0x0002
0x0004
0x0001
CC
reset protection circuit can be
CC
. This will pre-
7674F–AVR–09/09