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 67 shows typical USB IN and OUT transactions reporting the split in the hard-
ware (UFI) and software (C51) load.
Figure 66. UFI Block Diagram
USBCON
USBADDR
USBINT
USBIEN
UEPNUM
UEPCONX
Transfer
Control
FSM
Asynchronous Information
UEPSTAX
UEPRST
UEPINT
12 MHz DPLL
To/From C51 Core
UEPIEN
UEPDATX
UBYCTX
UFNUMH
UFNUML
Endpoint 2
Endpoint 1
Endpoint 0
Endpoint Control
USB side
Endpoint Control
C51 side
To/From SIE
Figure 67. USB Typical Transaction Load
OUT Transactions:
OUT DATA0 (n Bytes)
OUT
DATA1
OUT
ACK
DATA1
HOST
UFI
ACK C51 interrupt
NACK
ACK
Endpoint FIFO read (n Bytes)
C51
IN Transactions:
IN
IN
IN
HOST
NACK
Endpoint FIFO Write
DATA1
DATA1
UFI
C51 interrupt
Endpoint FIFO write
C51
106
AT8xC51SND2C
4341D–MP3–04/05
ATMEL [ ATMEL ]
