ATmega64 Atmel Corporation, ATmega64 Datasheet - Page 284

• Manufacturer Part Number: ATmega64
• Manufacturer: Atmel Corporation

Specifications of ATmega64

• Flash (kbytes): 64 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 53
• Ext Interrupts: 8
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 2048
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 8
• Input Capture Channels: 2
• Pwm Channels: 7
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

Self-programming
the Flash
Performing Page
Erase by SPM
Filling the Temporary
Buffer (Page Loading)
Performing a Page
Write
2490Q–AVR–06/10
The program memory is updated in a page-by-page fashion. Before programming a page with
the data stored in the temporary page buffer, the page must be erased. The temporary page buf-
fer is filled one word at a time using SPM and the buffer can be filled either before the Page
Erase command or between a Page Erase and a Page Write operation:
Alternative 1, fill the buffer before a Page Erase:
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•
•
Alternative 2, fill the buffer after Page Erase:
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•
•
If only a part of the page needs to be changed, the rest of the page must be stored (for example
in the temporary page buffer) before the erase, and then be rewritten. When using Alternative 1,
the boot loader provides an effective Read-Modify-Write feature which allows the user software
to first read the page, do the necessary changes, and then write back the modified data. If Alter-
native 2 is used, it is not possible to read the old data while loading since the page is already
erased. The temporary page buffer can be accessed in a random sequence. It is essential that
the page address used in both the Page Erase and Page Write operation is addressing the same
page. See
code example.
To execute Page Erase, set up the address in the Z-pointer, write “X0000011” to SPMCSR and
execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored.
The page address must be written to PCPAGE in the Z-register. Other bits in the Z-pointer must
be written zero during this operation.
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•
Note:
To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write
“00000001” to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The
content of PCWORD in the Z-register is used to address the data in the temporary buffer. The
temporary buffer will auto-erase after a Page Write operation or by writing the RWWSRE bit in
SPMCSR. It is also erased after a System Reset. Note that it is not possible to write more than
one time to each address without erasing the temporary buffer.
Note:
To execute Page Write, set up the address in the Z-pointer, write “X0000101” to SPMCSR and
execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored.
The page address must be written to PCPAGE. Other bits in the Z-pointer must be written zero
during this operation.
•
•
Fill temporary page buffer
Perform a Page Erase
Perform a Page Write
Perform a Page Erase
Fill temporary page buffer
Perform a Page Write
Page Erase to the RWW section: The NRWW section can be read during the Page Erase.
Page Erase to the NRWW section: The CPU is halted during the operation.
Page Write to the RWW section: The NRWW section can be read during the Page Write.
Page Write to the NRWW section: The CPU is halted during the operation.
If an interrupt occurs in the timed sequence, the four cycle access cannot be guaranteed. In order
to ensure atomic operation disable interrupts before writing to SPMCSR.
If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded will be
lost.
“Simple Assembly Code Example for a Boot Loader” on page 287
ATmega64(L)
for an assembly
284