AT43USB325 datasheet(55/109 Pages) ATMEL

55 / 109 page

3355C–USB–4/05

AT43USB325

I/O Ports

All GPIO ports have true Read-Modify-Write functionality when used as general digital I/O ports.

This means that the direction of one port pin can be changed without unintentionally changing

the direction of any other pin with the SBI and CBI instructions. The same applies for changing

drive value if configured as output or enabling/disabling of pull-up resistors if configured as input.

The keyboard matrix strobe output pins, PA[0:7], PB[0:7] and PE[0:3] have controlled slope driv-

ers. With a load of 100 pF, the output fall time ranges between 75 ns and 300 ns. The keyboard

matrix strobe input pins, PC[0:7] have When the FE3 IMSK bit is set (1), the Function End-point

3 Interrupt is masked.

PE[4:7] have 5V tolerant outputs and each has a built-in series resistor of 330

Ω nominal value.

These output pins are designed for driving an LED connected to the 5V supply.

The dedicated functions are summarized in Table 7-1.

In the AT43USB325E Port F[0:3] are used as the SPI signals for the external serial EEPROM.

Once the data from the SEEPROM are loaded to the SRAM, Port F[1:3] become available as

GPIO pins. Only cycling the power to the chip off and on again will temporarily assign these pins

as EEPOM signals.

Table 7-1.

GPIO Function Assignments

Function

GPIO

Scan out[0:7]

PA[0:7]

Scan out[8:15]

PB[0:7]

Scan out[16:19]

PE[0:3]

Scan in[0:7]

PC[0:7]

LED drivers

PE[4:7]

EEPROM Interface

PF[1:3]

AT43USB325 Datasheet(PDF) 55 Page - ATMEL Corporation