ATMEGA640 datasheet(340/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

3. The serial programming instructions will not work if the communication is out of synchronization. When in

sync. the second byte (0x53), will echo back when issuing the third byte of the Programming Enable

instruction. Whether the echo is correct or not, all four bytes of the instruction must be transmitted. If the

0x53 did not echo back, give RESET a positive pulse and issue a new Programming Enable command.

4. The Flash is programmed one page at a time. The memory page is loaded one byte at a time by supplying

the 7 LSB of the address and data together with the Load Program Memory Page instruction. To ensure

correct loading of the page, the data low byte must be loaded before data high byte is applied for a given

address. The Program Memory Page is stored by loading the Write Program Memory Page instruction with

the address lines 15:8. Before issuing this command, make sure the instruction Load Extended Address

Byte has been used to define the MSB of the address. The extended address byte is stored until the com-

mand is re-issued, that is, the command needs only be issued for the first page, and when crossing the

64KWord boundary. If polling (RDY/BSY) is not used, the user must wait at least tWD_FLASH before issuing the

next page (see Table 30-16). Accessing the serial programming interface before the Flash write operation

completes can result in incorrect programming.

5. The EEPROM array is programmed one byte at a time by supplying the address and data together with the

appropriate Write instruction. An EEPROM memory location is first automatically erased before new data is

written. If polling is not used, the user must wait at least tWD_EEPROM before issuing the next byte (see Table

30-16). In a chip erased device, no 0xFFs in the data file(s) need to be programmed.

6. Any memory location can be verified by using the Read instruction which returns the content at the selected

address at serial output PDO. When reading the Flash memory, use the instruction Load Extended Address

Byte to define the upper address byte, which is not included in the Read Program Memory instruction. The

extended address byte is stored until the command is re-issued, that is, the command needs only be issued

for the first page, and when crossing the 64KWord boundary.

7. At the end of the programming session, RESET can be set high to commence normal operation.

8. Power-off sequence (if needed):

Set RESET to “1”.

Turn VCC power off.

30.8.3

Serial Programming Instruction set

Table 30-17 and Figure 30-11 on page 342 describes the Instruction set.

Table 30-16. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location

Symbol

Minimum Wait Delay

tWD_FLASH

4.5ms

tWD_EEPROM

3.6ms

tWD_ERASE

9.0ms

Table 30-17. Serial Programming Instruction Set

Instruction/Operation

Instruction Format

Byte 1

Byte 2

Byte 3

Byte 4

Programming Enable

$AC

$53

$00

Chip Erase (Program Memory/EEPROM)

$AC

$80

$00

Poll RDY/BSY

$F0

$00

data byte out

Load Instructions

Load Extended Address byte(1)

$4D

$00

Extended adr

$00

Load Program Memory Page, High byte

$48

$00

adr LSB

high data byte in

Load Program Memory Page, Low byte

$40

$00

adr LSB

low data byte in

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