Datasheet

268
7766F–AVR–11/10
ATmega16/32U4
Figure 22-2. 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 is will not be sent if the Endpoint size parameter is bigger than the DPRAM size.
A clear of EPEN acts as an endpoint reset (see Section 22.3, page 266 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 Section 21.9, page 260 for more details about the memory allocation/reorganization.
22.7 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 handles this request, and records that address in UADD, but keep ADDEN
cleared,
• the USB device firmware sends an IN command of 0 bytes (IN 0 Zero Length Packet),
• then, the firmware can 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.
UADD contains the default address 00h after a power-up or USB reset.
Endpoint
Activation
CFGOK=1
ERROR
No
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