atmega32u4-16mu ATMEL Corporation, atmega32u4-16mu Datasheet - Page 280

• Manufacturer Part Number: atmega32u4-16mu
• Description: Atmega32u4 8-bit Avr Microcontroller With 32k Bytes Of Isp Flash And Usb Controller
• Manufacturer: ATMEL Corporation

22.8
280
PAD suspend
ATmega32U4
EPEN=1
ALLOC=1
The following figure illustrates the allocation and reorganization of the USB memory in a typical
example:
Table 22-1.
Note that:
The next figures illustrates the pad behaviour:
• First, Endpoint 0 to Endpoint 5 are configured, in the growing order. The memory of each is
• Then, the Endpoint 3 is disabled (EPEN=0), but its memory reservation is internally kept by
• Its ALLOC bit is cleared: the Endpoint 4 “slides” down, but the Endpoint 5 does not “slide”.
• Finally, if the firmware chooses to reconfigure the Endpoint 3, with a bigger size. The
• the data of Endpoint 0 are never lost whatever the activation or deactivation of the higher
• Deactivate and reactivate the same Endpoint with the same parameters does not lead to a
• CFGOK is set by hardware even in the case where there is a “conflict” in the memory
• In the “idle” mode, the pad is put in low power consumption mode.
• In the “active” mode, the pad is working.
Free memory
Endpoints
reserved in the DPRAM.
the controller.
controller reserved the memory after the Endpoint 2 memory and automatically “slide” the
Endpoint 4. The Endpoint 5 does not move and a memory conflict appear, in that both
Endpoint 4 and 5 use a common area. The data of those endpoints are potentially lost.
Endpoint. Its data is lost if it is deactivated.
“slide” of the higher endpoints. For those endpoints, the data are preserved.
allocation.
activation
5
4
3
2
1
0
Allocation and reorganization USB memory flow
Endpoint Disable
Free memory
(ALLOC=1)
EPEN=0
5
4
2
1
0
Free its memory
Free memory
Lost memory
(ALLOC=0)
5
4
2
1
0
3 (bigger size)
Free memory
Activatation
Endpoint
4
2
1
0
5
7766A–AVR–03/08
Conflict