Register Map
13-17
USB Function Module
13.2.5 Status Register (STAT_FLG)
The read-only status flag register provides a status of the FIFO and the results
of the transaction handshakes for the selected endpoint. The eight MSB are
reserved for isochronous endpoints, while the eight LSB are reserved for non-
isochronous endpoints. This register cannot be read if EP_Sel bit is not
asserted for the endpoint. No status flag exists for the read-only setup FIFO,
which is always enabled.
The updates for non-isochronous transactions are done at the end of
each non-transparent and valid transaction to a given endpoint, if no
interrupt is pending on the endpoint.
Note:
Non-transparent, non-isochronous IN transactions are those transactions
responding with an ACK handshake, a STALL handshake, or optionally a
NAK handshake if the Nak_En bit is asserted to 1. An ERR handshake or a
NAK handshake when the Nak_En bit is 0 is considered transparent.
A write to this register has no effect.
Table 13–6. Status Register (STAT_FLG)
Bit
Name
Description
15
–
Reserved
14
Miss_In
Isochronous missed IN token for the previous frame (isochronous IN)
13
Data_Flush
Isochronous receive data flush (isochronous OUT)
12
ISO_Err
Isochronous receive data error (isochronous OUT)
11–10
–
Reserved
9
ISO_FIFO_Empty
Isochronous FIFO empty
8
ISO_FIFO_Full
Isochronous FIFO full
7
–
Reserved
6
EP_Halted
Endpoint halted flag (non-isochronous)
5
STALL
Transaction stall (non-isochronous)
4
NAK
Transaction non-acknowledge (non-isochronous)
