AT90USB646 datasheet(259/434 Pages) ATMEL

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7593A–AVR–02/06

AT90USB64/128

clear ALLOC. Then, the “ki+1” Pipe/Endpoint memory automatically “slides” down. Note that the

“k

i+2” and upper Pipe/Endpoint memory does not slide.

The following figure illustrates the allocation and reorganization of the USB memory in a typical

example:

Table 21-1.

Allocation and reorganization USB memory flow

• First, Pipe/Endpoint 0 to Pipe/Endpoint 5 are configured, in the growing order. The memory of

each is reserved in the DPRAM.

• Then, the Pipe/Endpoint 3 is disabled (EPEN=0), but its memory reservation is internally kept

by the controller.

• Its ALLOC bit is cleared: the Pipe/Endpoint 4 “slides” down, but the Pipe/Endpoint 5 does not

“slide”.

• Finally, if the firmware chooses to reconfigure the Pipe/Endpoint 3, with a bigger size. The

controller reserved the memory after the endpoint 2 memory and automatically “slide” the

Pipe/Endpoint 4. The Pipe/Endpoint 5 does not move and a memory conflict appear, in that

both Pipe/Endpoint 4 and 5 use a common area. The data of those endpoints are potentially

lost.

Note that:

• the data of Pipe/Endpoint 0 are never lost whatever the activation or deactivation of the

higher Pipe/Endpoint. Its data is lost if it is deactivated.

• Deactivate and reactivate the same Pipe/Endpoint with the same parameters does not lead

to a “slide” of the higher endpoints. For those endpoints, the data are preserved.

• CFGOK is set by hardware even in the case that there is a “conflict” in the memory allocation.

21.9 PAD suspend

The next figures illustrates the pad behaviour:

• In the “idle” mode, the pad is put in low power consumption mode.

• In the “active” mode, the pad is working.

Free memory

EPEN=1

ALLOC=1

Free memory

EPEN=0

(ALLOC=1)

Free memory

Pipe/Endpoints

activation

Pipe/Endpoint

Disable

Free its memory

(ALLOC=0)

Free memory

3 (bigger size)

Pipe/Endpoint

Activatation

Lost memory

Conflict

AT90USB646 Datasheet(PDF) 259 Page - ATMEL Corporation

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