Communication Processor Module
MOTOROLA MPC823e REFERENCE MANUAL 16-355
USB
COMMUNICATION
16
PROCESSOR MODULE
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.
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.
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.
Figure 16-113. USB Controller Operating Modes
RESET
UNENUMERATED
IDLE
SETUP
TRANSMIT RECEIVE
SOF
SETUP
TOKEN
IN
TOKEN
OUT
TOKEN
SOF
TOKEN
ENUMERATION
PROCESS
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