Register Descriptions
1334
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
M3 Universal Serial Bus (USB) Controller
18.5.29 USB Control and Status Endpoint 0 Low Register (USBCSRL0), offset 0x102
The USB control and status endpoint 0 low 8-bit register (USBCSRL0) provides control and status bits for
endpoint 0.
Mode(s):
OTG A or Host
OTG B or Device
USBCSRL0 in OTG A/Host mode is shown in
and described in
Figure 18-34. USB Control and Status Endpoint 0 Low Register (USBCSRL0) in OTG A/Host Mode
7
6
5
4
3
2
1
0
NAKTO
STATUS
REQPKT
ERROR
SETUP
STALLED
TXRDY
RXRDY
R/W-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 18-37. USB Control and Status Endpoint 0 Low Register(USBCSRL0)
in OTG A/Host Mode Field Descriptions
Bit
Field
Value
Description
7
NAKTO
NAK Timeout. Software must clear this bit to allow the endpoint to continue.
0
No timeout
1
Indicates that endpoint 0 is halted following the receipt of NAK responses for longer than the time set by
the USBNAKLMT register.
6
STATUS
Status Packet. Setting this bit ensures that the DT bit is set in the USBCSRH0 register so that a DATA1
packet is used for the STATUS stage transaction.
0
No transaction
1
Initiates a STATUS stage transaction. This bit must be set at the same time as the TXRDY or REQPKT
bit is set.
This bit is automatically cleared when the STATUS stage is over.
5
REQPKT
Request Packet. This bit is cleared when the RXRDY bit is set.
0
No request
1
Requests an IN transaction.
4
ERROR
Error. Software must clear this bit.
0
No error
1
Three attempts have been made to perform a transaction with no response from the peripheral. The
EP0 bit in the USBTXIS register is also set in this situation.
3
SETUP
Setup Packet. Setting this bit always clears the DT bit in the USBCSRH0 register to send a DATA0
packet.
0
Sends an OUT token.
1
Sends a SETUP token instead of an OUT token for the transaction. This bit should be set at the same
time as the TXRDY bit is set.
2
STALLED
Endpoint Stalled. Software must clear this bit.
0
No handshake has been received.
1
A STALL handshake has been received.
1
TXRDY
Transmit Packet Ready. If both the TXRDY and SETUP bits are set, a setup packet is sent. If just
TXRDY is set, an OUT packet is sent.
0
No transmit packet is ready.
1
Software sets this bit after loading a data packet into the TX FIFO. The EP0 bit in the USBTXIS register
is also set in this situation.
0
RXRDY
Receive Packet Ready. Software must clear this bit after the packet has been read from the FIFO to
acknowledge that the data has been read from the FIFO.
0
No receive packet has been received.
1
Indicates that a data packet has been received in the RX FIFO. The EP0 bit in the USBTXIS register is
also set in this situation.
USBCSRL0 in OTG B/Device mode is shown in
and described in