ATmega328P datasheet(309/448 Pages) ATMEL

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309

8161D–AVR–10/09

ATmega48PA/88PA/168PA/328P

27.8.1

Serial Programming Pin Mapping

27.8.2

Serial Programming Algorithm

When writing serial data to the ATmega48PA/88PA/168PA/328P, data is clocked on the rising

edge of SCK.

When reading data from the ATmega48PA/88PA/168PA/328P, data is clocked on the falling

edge of SCK. See Figure 27-9 for timing details.

To program and verify the ATmega48PA/88PA/168PA/328P in the serial programming mode,

the following sequence is recommended (See Serial Programming Instruction set in Table 27-19

on page 310):

Power-up sequence:

Apply power between V

CC and GND while RESET and SCK are set to “0”. In some sys-

tems, the programmer can not guarantee that SCK is held low during power-up. In this

case, RESET must be given a positive pulse of at least two CPU clock cycles duration

after SCK has been set to “0”.

Wait for at least 20 ms and enable serial programming by sending the Programming

Enable serial instruction to pin MOSI.

The serial programming instructions will not work if the communication is out of synchro-

nization. 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.

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

time by supplying the 6 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 7 MSB of

the address. If polling (RDY/BSY) is not used, the user must wait at least t

WD_FLASH before

issuing the next page (See Table 27-18). Accessing the serial programming interface

before the Flash write operation completes can result in incorrect programming.

A: 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 (RDY/BSY) is not used, the

user must wait at least t

WD_EEPROM before issuing the next byte (See Table 27-18). In a

chip erased device, no 0xFFs in the data file(s) need to be programmed.

B: The EEPROM array is programmed one page at a time. The Memory page is loaded

one byte at a time by supplying the 6 LSB of the address and data together with the Load

EEPROM Memory Page instruction. The EEPROM Memory Page is stored by loading

the Write EEPROM Memory Page Instruction with the 7 MSB of the address. When using

EEPROM page access only byte locations loaded with the Load EEPROM Memory Page

instruction is altered. The remaining locations remain unchanged. If polling (RDY/BSY) is

Table 27-17. Pin Mapping Serial Programming

Symbol

Pins

I/O

Description

MOSI

PB3

Serial Data in

MISO

PB4

Serial Data out

SCK

PB5

Serial Clock

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