ATmega16U2 datasheet(199/314 Pages) ATMEL

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199

7799B–AVR–07/09

ATmega8U2/16U2/32U2

Figure 21-2. Endpoint activation flow:

As long as the endpoint is not correctly configured (CFGOK cleared), the hardware does not

acknowledge the packets sent by the host.

CFGOK will not be set if the Endpoint size parameter is bigger than the DPRAM size.

A clear of EPEN acts as an endpoint reset (see “Endpoint reset” on page 197 for more details).

It also performs the next operation:

• The configuration of the endpoint is kept (EPSIZE, EPBK, ALLOC kept)

• It resets the data toggle field.

• The DPRAM memory associated to the endpoint is still reserved.

See “Memo ry ma nagem ent” on p age 192 for more details abou t the mem o ry

allocation/reorganization.

21.7

Address Setup

The USB device address is set up according to the USB protocol:

• the USB device, after power-up, responds at address 0

• the host sends a SETUP command (SET_ADDRESS(addr)),

• the firmware records that address in UADD, but keep ADDEN cleared,

• the USB device sends an IN command of 0 bytes (IN 0 Zero Length Packet) to acknowledge

the transaction,

• then, the firmware may enable the USB device address by setting ADDEN. The only

accepted address by the controller is the one stored in UADD.

ADDEN and UADD shall not be written at the same time.

Endpoint

Activation

CFGOK=1

ERROR

Yes

Endpoint activated

Activate the endpoint

Select the endpoint

EPEN=1

UENUM

EPNUM=x

Test the correct endpoint

configuration

UECFG1X

ALLOC

EPSIZE

EPBK

Configure:

- the endpoint size

- the bank parametrization

Allocation and reorganization of

the memory is made on-the-fly

UECFG0X

EPDIR

EPTYPE

...

Configure:

- the endpoint direction

- the endpoint type

- the Not Yet Disable feature

ATmega16U2 Datasheet(PDF) 199 Page - ATMEL Corporation

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