ATMEGA32U4RC-AU(2016) View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATMEGA32U4RC-AU
(Rev.:2016)

8-bit Microcontroller with 16/32K bytes of ISP Flash and USB Controller

Atmel Corporation 

28.8 Serial Programming Pin Mapping

Table 28-14. Pin Mapping Serial Programming

Symbol

PDI

PDO

SCK

Pins (TQFP-64)

PB2

PB3

PB1

Figure 28-10. Serial Programming and Verify(1)

PDI

PDO

SCK

XTAL1

I/O

Description

I

Serial Data in

O

Serial Data out

I

Serial Clock

+1.8 - 5.5V

VCC

+1.8 - 5.5V(2)

AVCC

RESET

GND

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:> two CPU clock cycles for fck < 12MHz, three CPU clock cycles for fck >= 12MHz

High:> two CPU clock cycles for fck < 12MHz, three CPU clock cycles for fck >= 12MHz

28.8.1 Serial Programming Algorithm

When writing serial data to the device, data is clocked on the rising edge of SCK.

When reading data from the device, data is clocked on the falling edge of SCK. See Figure 28-11 on page 369

for timing details.

To program and verify the device in the serial programming mode, the following sequence is recommended (see

four byte instruction formats in Table 28-16 on page 370):

1. Power-up sequence:

Apply power between VCC and GND while RESET and SCK are set to “0”. In some systems, the pro-

grammer 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”.

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

instruction to pin PDI.

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

ATmega16U4/32U4 [DATASHEET]

Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016

368

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