Rainbow Electronics AT89C51SND1C - Manual (Page 83)

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AT8xC51SND1C
4109E–8051–06/03
Function Interface Unit (UFI) The Function Interface Unit provides the interface between the AT8xC51SND1C 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 59 shows typical USB IN and OUT transactions reporting the split in the hard-
ware (UFI) and software (C51) load.
Figure 58. UFI Block Diagram
Figure 59. USB Typical Transaction Load
To/From C51 Core
Endpoint Control
C51 side
Endpoint Control
USB side
Endpoint 2
Endpoint 1
Endpoint 0
USBCON
USBINT
USBIEN
UEPINT
UEPIEN
UEPNUM
UEPSTAX
USBADDR
UEPCONX
UEPDATX
UEPRST
UBYCTX
UFNUMH
UFNUML
Asynchronous Information
Transfer
Control
FSM
To/From SIE
12 MHz DPLL
OUT Transactions:
HOST
UFI
C51
OUT DATA0 (n Bytes)
ACK
Endpoint FIFO read (n Bytes)
OUT DATA1
NACK
OUT DATA1
ACK
IN Transactions:
HOST
UFI
C51
IN ACK
Endpoint FIFO Write
IN
DATA1 NACK
C51 interrupt
IN
DATA1 C51 interrupt
Endpoint FIFO write