Register Descriptions
1340
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Universal Serial Bus (USB) Controller
Table 18-44. USB Transmit Control and Status Endpoint n Low Register (USBTXCSRL[n])
in OTG A/Host Mode Field Descriptions (continued)
Bit
Field
Value
Description
0
TXRDY
Transmit Packet Ready.
This bit is cleared automatically when a data packet has been transmitted. The EP
n
bit in the USBTXIS
register is also set at this point. TXRDY is also automatically cleared prior to loading a second packet
into a double-buffered FIFO.
0
No transmit packet is ready.
1
Software sets this bit after loading a data packet into the TX FIFO.
The USBTXCSRL[
n
] registers in OTG B/Device Mode are shown in
and described in
.
Figure 18-42. USB Transmit Control and Status Endpoint n Low Register (USBTXCSRL[n])
in OTG B/Device Mode
7
6
5
4
3
2
1
0
Reserved
CLRDT
STALLED
STALL
FLUSH
UNDRN
FIFONE
TXRDY
R-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
LEGEND: R/W = Read/Write; -
n
= value after reset
Table 18-45. USB Transmit Control and Status Endpoint n Low Register (USBTXCSRL[n])
in OTG B/Device Mode Field Descriptions
Bit
Field
Value
Description
7
Reserved
0
Reserved
6
CLRDT
Clear Data Toggle
0
No effect
1
Writing a 1 to this bit clears the DT bit in the USBTXCSRH[
n
] register.
5
STALLED
Endpoint Stalled. Software must clear this bit.
0
A STALL handshake has not been transmitted.
1
A STALL handshake has been transmitted. The FIFO is flushed and the TXRDY bit is cleared.
4
STALL
Send Stall. Software clears this bit to terminate the STALL condition.
Note:
This bit has no effect in isochronous transfers.
0
No effect
1
Issues a STALL handshake to an IN token.
3
FLUSH
Flush FIFO. This bit may be set simultaneously with the TXRDY bit to abort the packet that is currently
being loaded into the FIFO. Note that if the FIFO is double-buffered, FLUSH may have to be set twice
to completely clear the FIFO.
Note:
This bit should only be set when the TXRDY bit is set. At other times, it may cause data to be
corrupted.
0
No effect
1
Flushes the latest packet from the endpoint transmit FIFO. The FIFO pointer is reset and the TXRDY bit
is cleared. The EPn bit in the USBTXIS register is also set in this situation.
This bit is cleared automatically.
2
UNDRN
Underrun. Software must clear this bit.
0
No underrun
1
An IN token has been received when TXRDY is not set.
1
FIFONE
FIFO Not Empty
0
The FIFO is empty.
1
At least one packet is in the transmit FIFO.