Motorola MPC823e Reference Manual page 809

16.10.4 Transmission and Reception Process
After reset, the USB controller is addressable at the default address (0x00). During the
enumeration process, the host assigns a unique address to the USB controller. The software
must program the USB address register with the assigned address. The USB controller
supports four independent endpoints, which can each be configured to support control,
interrupt, bulk, or isochronous transfers modes when you program the USB endpoint
registers.
Note: You must configure endpoint 0 as a control transfer type. This endpoint is used
by the USB system software as a control pipe and any additional control pipes
may be provided by other endpoints.
Once enabled, the USB controller looks for valid token packets. Tokens that are not valid
(the PID or CRC check fails or the packet length is not 3 bytes) are ignored.
SETUP
Figure 16-113. USB Controller Operating Modes
MOTOROLA
RESET
UNENUMERATED
ENUMERATION
PROCESS
IDLE
SETUP
TOKEN
IN
TOKEN TOKEN
TRANSMIT RECEIVE
MPC823e REFERENCE MANUAL
Communication Processor Module
SOF
TOKEN
OUT
SOF
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