USB Device Controller
1566
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Universal Serial Bus (USB)
Table 29-34. Control Register (CTRL) Field Descriptions (continued)
Bit
Field
Value
Description
0
RESET_EP
The endpoint reset (non-control) bit only concerns non-control endpoints. The USB device controller
sets this bit to reset the selected endpoint. It forces an interrupt or a bulk endpoint data PID to
DATA0, clears the halt condition, and clears the FIFO (both foreground and background if endpoint
is double-buffered) and previous transactions handshake status. For an ISO endpoint, it only clears
the FIFO (both foreground and background).
0
No action
1
Reset endpoint
Always read 0.
29.3.1.5 Status Register (STAT_FLG)
This read-only register provides a status of the FIFO and the results of the transactions handshakes for
the selected endpoint. The 8 MSB are reserved for ISO endpoints, whereas the 8 LSB are reserved for
non-ISO endpoints. This register cannot be read if EP_NUM.EP_SEL bit is not asserted for the endpoint.
No status flag exists for the read-only set-up FIFO, which is always enabled.
NOTE:
The updates for non-ISO transactions are done at the end of each non-transparent and valid
transaction to a given endpoint, if no non-handled interrupt is pending on the endpoint.
The definition of a non-transparent, non-ISO IN transaction is one that responds with an ACK
handshake or a STALL handshake, or optionally a NAK handshake if SYSCON1.NAK_EN is
asserted to 1. An ERR handshake or a NAK handshake when SYSCON1.NAK_EN is 0 is
considered transparent.
A write to this register has no effect.
Figure 29-32. Status Register (STAT_FLG) [address = FCF78A08h]
15
14
13
12
11
10
9
8
NO_RX-
PACKET
MISS_IN
DATA_FLUSH
ISO_ERR
Reserved
ISO_FIFO_
EMPTY
ISO_FIFO_
FULL
R-0
R-0
R-0
R-0
R-0
R-0
R-0
7
6
5
4
3
2
1
0
Reserved
EP_HALTED
STALL
NAK
ACK
FIFO_EN
NON_ISO_
FIFO_EMPTY
NON_ISO_
FIFO_FULL
R-0
R-0
R-0
R-0
R-0
R-0
R-0
R-0
LEGEND: R = Read only; -
n
= value at reset
Table 29-35. Status Register (STAT_FLG) Field Descriptions
Bit
Field
Value
Description
15
NO_RXPACKET
The isochronous no packet received (ISO OUT) bit only concerns ISO OUT endpoints. This
bit notifies the USB device controller that the core has not received any isochronous packet
on the endpoint. This bit is updated on a SOF (start of frame).
0
The endpoint received a packet on the previous frame.
1
The endpoint did not receive a packet on the previous frame.
Value after system reset or USB reset is high.