ATmega328P datasheet(308/448 Pages) ATMEL

308 / 448 page

308

8161D–AVR–10/09

ATmega48PA/88PA/168PA/328P

27.7.14

Reading the Calibration Byte

The algorithm for reading the Calibration byte is as follows (refer to ”Programming the Flash” on

page 302 for details on Command and Address loading):

A: Load Command “0000 1000”.

B: Load Address Low Byte, 0x00.

Set OE to “0”, and BS1 to “1”. The Calibration byte can now be read at DATA.

Set OE to “1”.

27.7.15

Parallel Programming Characteristics

For chracteristics of the Parallel Programming, see ”Parallel Programming Characteristics” on

page 324.

27.8

Serial Downloading

Both the Flash and EEPROM memory arrays can be programmed using the serial SPI bus while

RESET is pulled to GND. The serial interface consists of pins SCK, MOSI (input) and MISO (out-

put). After RESET is set low, the Programming Enable instruction needs to be executed first

before program/erase operations can be executed. NOTE, in Table 27-17 on page 309, the pin

mapping for SPI programming is listed. Not all parts use the SPI pins dedicated for the internal

SPI interface.

Figure 27-7. Serial Programming and Verify(1)

Notes:

1. If the device is clocked by the internal Oscillator, it is no need to connect a clock source to the

XTAL1 pin.

2. VCC - 0.3V < AVCC < VCC + 0.3V, however, AVCC should always be within 1.8 - 5.5V

When programming the EEPROM, an auto-erase cycle is built into the self-timed programming

operation (in the Serial mode ONLY) and there is no need to first execute the Chip Erase

instruction. The Chip Erase operation turns the content of every memory location in both the

Program and EEPROM arrays into 0xFF.

Depending on CKSEL Fuses, a valid clock must be present. The minimum low and high periods

for the serial clock (SCK) input are defined as follows:

Low: > 2 CPU clock cycles for f

ck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz

High: > 2 CPU clock cycles for f

ck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz

VCC

GND

XTAL1

SCK

MISO

MOSI

RESET

+1.8 - 5.5V

AVCC

+1.8 - 5.5V

(2)

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