at43usb355 ATMEL Corporation, at43usb355 Datasheet - Page 10

• Manufacturer Part Number: at43usb355
• Description: At43usb355 Full-speed Usb Microcontroller With Embedded Hub, Adc And Pwm
• Manufacturer: ATMEL Corporation

SPI Serial
EEPROM Interface
(AT43USB355E
Only)
Read Sequence
10
AT43USB355
The program memory of the AT43USB355E is automatically written with data stored in an
external serial EEPROM during the chip's power-on reset sequence. The power-on reset is
the only way the on-chip program memory of the AT43USB355E will be written or modified.
The two versions of the AT43USB355 are binary compatible. A firmware written for the
AT43USB355E will work unaltered on the AT43USB355M. The only functional difference
between the two versions is with respect to the serial EEPROM interface pins, GPIO PF[0:3].
The differences are:
The AT43USB355E is designed to interface directly with a synchronous serial peripheral inter-
face (SPI) SEEPROM such as the Atmel AT25HP256/512. All instructions, addresses and
data are transferred with the MSB first and start with a high-to-low SSN transition.
Note:
Figure 4. AT43USB355E Read Sequence
1. The AT43USB35E asserts its SSN output pin and outputs a 3 MHz clock at SCK. It
2. The AT43USB355E transmits the READ op-code (= 0000011) through its MOSI, fol-
3. The SEEPROM then shifts out the data through its MISO pin.
4. The AT43USB35E de-asserts SCK and SSN after 24K bytes data read is complete.
Port F Pins
PF0
PF1, PF2, PF3
continues to activate SCK until the completion of the read process.
lowed by the 16-bit byte address to be read, x0000. Please note that the
AT43USB355E will send a 16-byte address only. SEEPROM with SPI that requires a
24-bit address cannot be used with the AT43USB355E.
The SPI port of the AT43USB355E at PF[0:3] is dedicated for program memory downloading
only. It cannot be accessed by the firmware program.
AT43USB355E
AT43USB355E
Slave Select Pin – Its output will be asserted (low) during
downloading of firmware and will stay de-asserted (high) after
download is completed.
Functions as serial EEPROM interface signals during
downloading and as GPIO pins after download is completed.
MOSI
MISO
SSN
SCK
AT25HP256
AT43USB355M
NC (No connect)
GPIO
2603G–USB–04/06