XR21B1420 Datasheet, PDF (23/60 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed USB UART

XR21B1420
Bit
5
4
3
2:0
Default
Description
0
Parity Error
0: No parity error.
1: A parity error has been detected (clears after read).
0
Framing Error
0: No framing error.
1: A framing error has been detected (clears after read). A framing error occurs when a stop bit is not present
when it is expected.
0
Break Error
0: No break condition.
1: A break condition has been detected (clears after read).
0
Reserved
These bits are reserved and should be written as ‘0’.
TX_BREAK (0x00A) - Read/Write
This register controls UART TX break signaling.
Bit
15:0
Default
Description
0
Value
For value TX_BREAK value of N: If N == 0xFFFF, the UART TX outputs a continuous break signal. If 0x0000 <
N < 0xFFFF (a maximum of 64,534 ms), the UART TX outputs a break signal that lasts N ms, and the register
serves as a counter, counting down to 0, decrementing by 1 every millisecond. If N == 0x0000, the UART TX
stops sending the break signal.
When the user writes to this register, any previous process is terminated, and the new command takes effect. If
data is being shifted out of the TX pin, the data will be completely shifted out before the break condition is gen-
erated.
NOTE: After this register is programmed from 0x0000 to a non-zero value, the UART TX may take up to, but no
more than 1 ms, before sending out the break condition. In addition, after the break counter decrements to zero,
the UART TX may take up to, but no more than 2 UART characters, based on the current UART configuration,
before stopping the break. Thus, the actual break length may be slightly longer than the programmed value, by
up to, but no more than (1ms + 2x UART-character-length).
XCVR_EN_DELAY (0x00B) - Read/Write
Bit
15:4
3:0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
Turn-around delay
Turn-around delay controls the number of bit times (0-15) to wait before changing the direction of the RS-485
half-duplex from transmit to receive when auto RS-485 half-duplex control is enabled. This allows for propaga-
tion of characters to complete across lengthy mediums.
© 2014 Exar Corporation
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Rev 1A