XR21B1422IL40-0A Datasheet, PDF (26/60 Pages) Exar Corporation – Enhanced 2-Ch Full-Speed USB UART

XR21B1422
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, count-
ing 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 generated.
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 propagation of characters to complete
across lengthy mediums.
GPIO_MODE (0x00C) - Read/Write
Bit
15:10
9
8
7
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
1
Receive Toggle
0: GPIO9 is used for general purpose I/O
1: GPIO9 is used to receive toggle output (default).
1
Transmit Toggle
0: GPIO8 is used for general purpose I/O.
1: GPIO8 is used to transmit toggle output (default).
0
Clock Enable
0: GPIO6 is used for general purpose I/O
1: GPIO6 is used to output a clock. See “OUTCLK (0x018) - Read/Write” on page 33.
© 2014 Exar Corporation
26 / 60
exar.com/XR21B1422
Rev 1A