Datasheet

105
4341H–MP3–10/07
AT8xC51SND2C/MP3B
16.3.2 Serial Interface Engine (SIE)
The SIE performs the following functions:
• NRZI data encoding and decoding.
• Bit stuffing and unstuffing.
• CRC generation and checking.
• ACKs and NACKs automatic generation.
• TOKEN type identifying.
• Address checking.
• Clock recovery (using DPLL).
Figure 16-4. SIE Block Diagram
16.3.3 Function Interface Unit (UFI)
The Function Interface Unit provides the interface between the AT8xC51SND2C and the SIE. It
manages transactions at the packet level with minimal intervention from the device firmware,
which reads and writes the endpoint FIFOs.
Figure 16-6 shows typical USB IN and OUT transactions reporting the split in the hardware (UFI)
and software (C51) load.
8
Start of Packet
Detector
Clock
Recover
SYNC Detector
PID Decoder
Address Decoder
Serial to Parallel
Converter
CRC5 & CRC16
Generator/Check
USB Pattern Generator
Parallel to Serial Converter
Bit Stuffing
NRZI Converter
CRC16 Generator
NRZI ‘ NRZ
Bit Unstuffing
Packet Bit Counter
End of Packet
Detector
USB
CLOCK
48 MHz
SysClk
Data In
D+
D-
(12 MHz)
8
Data Out