Atmel AT85DVK-07 Especificações descarregar pdf (Página 90)

AT85C51SND3Bx

7632A–MP3–03/06

When using this mode, there is no influence over the USB controller.

Memory Management The controller only supports the following memory allocation management:

The reservation of a Pipe or an Endpoint can only be made in the growing order

(Pipe/Endpoint 0 to the last Pipe/Endpoint). The firmware shall thus configure them in

the same order.

The reservation of a Pipe or an Endpoint “k

” is done when its ALLOC bit is set. Then,

the hardware allocates the memory and insert it between the Pipe/Endpoints “k

i-1

” and

“k

i+1

”. The “k

i+1

” Pipe/Endpoint memory “slides” up and its data is lost. Note that the “k

i+2

”

and upper Pipe/Endpoint memory does not slide.

Clearing a Pipe enable (PEN) or an Endpoint enable (EPEN) does not clear neither its

ALLOC bit, nor its configuration (EPSIZE/PSIZE, EPBK/PBK). To free its memory, the

firmware should clear ALLOC. Then, the “k

i+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:

Figure 54. Allocation and reorganization USB memory flow

Endpoint 0

Endpoint 1 to N

Unused

[DPADDH – DPADDL]

USB DPRAM

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

Conflic

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