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Serial Interface Engine (SIE)
The SIE is responsible for managing all transactions to the USB. It controls the bus protocol,
packet generation/extraction, data parallel-to-serial conversion, CRC coding, bit stuffing, and
NRZI encoding.
All transactions on the USB are requested by the List Processor and Frame Manager. After the List
Processor retrieves all information necessary to initiate communication to a USB device, it
generates a request to the SIE accompanied by endpoint specific control information required to
generate proper protocol and packet formats to establish the desired communication pipe. The data
buffer provides a data path for the data packets and controls the number of bytes transferred.
The FM generates SOF events each millisecond for which the SIE generates an SOF token. The
List Processor requests are ignored to allow the SOF to be serviced with the highest priority and no
delay.
SIE Control
Table 18-13 lists all other control information which is required to generate and manage the
requested transaction. Most of the information is extracted from the ED and TD in the List
Processor.
Table 18.13 Transaction Control Information
Information
Direction[1:0]
Format
Data Toggle State
Speed
EndpointNumber[3:0] The token endpoint data.
FunctionAddress[7:0] The token address data.
HcFmNumber [10:0]
Packet Control
The sections below describe the packet types and formats generated by the SIE.
1) Sync Pattern
The first byte of every packet is a synchronization pattern that allows the data receiver to
synchronize to the transmitters data rate prior to any meaningful data. The pattern 80h
translates into an NRZI encoding of 54h on the bus. The byte? ending sequence of KK signifies
the start of the PID byte.
Rev. 3.0, 03/01, page 294 of 390
Description
The data packet direction and PID must be defined as IN, OUT, SETUP.
The transaction must be identified as isochronous to remove the
handshake phase from the bus protocol.
The data toggle state is required for selecting PID DATA0 or DATA1 and
data toggle comparison. (ToggleCarry/DataToggle)
The endpoint speed is required to select the bus data rate.
The SOF token data field for device frame synchronization.
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