ATmega640 Atmel Corporation, ATmega640 Datasheet - Page 24
ATmega640
Manufacturer Part Number
ATmega640
Description
Manufacturer
Atmel Corporation
Specifications of ATmega640
Flash (kbytes)
64 Kbytes
Pin Count
100
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
86
Ext Interrupts
32
Usb Speed
No
Usb Interface
No
Spi
5
Twi (i2c)
1
Uart
4
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
16
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
8
Eeprom (bytes)
4096
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
6
Output Compare Channels
16
Input Capture Channels
4
Pwm Channels
15
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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Price
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8.3.1
2549N–AVR–05/11
EEPROM Read/Write Access
The EEPROM Access Registers are accessible in the I/O space, see
page
The write access time for the EEPROM is given in
lets the user software detect when the next byte can be written. If the user code contains instruc-
tions that write the EEPROM, some precautions must be taken. In heavily filtered power
supplies, V
period of time to run at a voltage lower than specified as minimum for the clock frequency used.
See “Preventing EEPROM Corruption” on page 26.
situations.
In order to prevent unintentional EEPROM writes, a specific write procedure must be followed.
See the description of the EEPROM Control Register for details on this;
on page
When the EEPROM is read, the CPU is halted for four clock cycles before the next instruction is
executed. When the EEPROM is written, the CPU is halted for two clock cycles before the next
instruction is executed.
The calibrated Oscillator is used to time the EEPROM accesses.
gramming time for EEPROM access from the CPU.
Table 8-1.
The following code examples show one assembly and one C function for writing to the
EEPROM. The examples assume that interrupts are controlled (for example by disabling inter-
rupts globally) so that no interrupts will occur during execution of these functions. The examples
also assume that no Flash Boot Loader is present in the software. If such code is present, the
EEPROM write function must also wait for any ongoing SPM command to finish.
Symbol
EEPROM write
(from CPU)
35.
35.
CC
is likely to rise or fall slowly on power-up/down. This causes the device for some
EEPROM Programming Time
Number of Calibrated RC Oscillator Cycles
ATmega640/1280/1281/2560/2561
26,368
for details on how to avoid problems in these
Table
8-1. A self-timing function, however,
Table 8-1
“Register Description” on
Typ Programming Time
“Register Description”
lists the typical pro-
3.3ms
24
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