21.4.23 EINCSRL: USB0 IN Endpoint Control Low
Bit
7
6
5
4
3
2
1
0
Name
Reserved
CLRDT
STSTL
SDSTL
FLUSH
UNDRUN
FIFONE
INPRDY
Access
R
W
RW
RW
RW
RW
RW
RW
Reset
0
0
0
0
0
0
0
0
Indirect Address: 0x11
Bit
Name
Reset
Access Description
7
Reserved
Must write reset value.
6
CLRDT
0
W
Clear Data Toggle.
5
STSTL
0
RW
Sent Stall Flag.
Hardware sets this bit to 1 when a STALL handshake signal is transmitted. The FIFO is flushed, and the INPRDY bit
cleared. This flag must be cleared by firmware.
4
SDSTL
0
RW
Send Stall.
Firmware should set this bit to 1 to generate a STALL handshake in response to an IN token. Firmware should clear this bit
to 0 to terminate the STALL signal. This bit has no effect in Isochronous mode.
3
FLUSH
0
RW
FIFO Flush.
Writing a 1 to this bit flushes the next packet to be transmitted from the IN Endpoint FIFO. The FIFO pointer is reset and the
INPRDY bit is cleared. If the FIFO contains multiple packets, firmware must write 1 to FLUSH for each packet. Hardware
resets the FLUSH bit to 0 when the FIFO flush is complete.
2
UNDRUN
0
RW
Data Underrun Flag.
The function of this bit depends on the IN Endpoint mode:
Isochronous: Set when a zero-length packet is sent after an IN token is received while bit INPRDY = 0.
Interrupt/Bulk: Set when a NAK is returned in response to an IN token.
This bit must be cleared by firmware.
1
FIFONE
0
RW
FIFO Not Empty.
Value
Name
Description
0
EMPTY
The IN Endpoint FIFO is empty.
1
NOT_EMPTY
The IN Endpoint FIFO contains one or more packets.
0
INPRDY
0
RW
In Packet Ready.
Firmware should write 1 to this bit after loading a data packet into the IN Endpoint FIFO. Hardware clears INPRDY due to
any of the following:
1. A data packet is transmitted.
2. Double buffering is enabled (DBIEN = 1) and there is an open FIFO packet slot.
3. If the endpoint is in Isochronous Mode (ISO = 1) and ISOUD = 1, INPRDY will read 0 until the next SOF is received.
An interrupt (if enabled) will be generated when hardware clears INPRDY as a result of a packet being transmitted.
This register is accessed indirectly using the USB0ADR and USB0DAT registers.
EFM8UB3 Reference Manual
Universal Serial Bus (USB0)
silabs.com
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