XR21B1411IL-0A-EB Datasheet, PDF (21/30 Pages) Exar Corporation – ENHANCED 1-CH FULL-SPEED USB UART

XR21B1411
REV. 1.2.0
ENHANCED 1-CH FULL-SPEED USB UART
3.1.1.20 PIN_PULLUP_EN Register Description (Read / Write)
PIN_PULLUP_EN[5:0]: GPI0[5:0]
Enables internal pullup feature on the selected GPIO pins
 Logic 0 = Disable pullup on the corresponding pin.
 Logic 1 = Enable pullup on the corresponding pin - Caution: Do not enable pulldown simultaneously
PIN_PULLUP_EN[6]: UART Rx
Enables internal pullup feature on the UART Rx pin
 Logic 0 = Disable pullup on the corresponding pin.
 Logic 1 = Enable pullup on the corresponding pin - Caution: Do not enable pulldown simultaneously
PIN_PULLUP_EN[7]: UART Tx
Enables internal pullup feature on the UART Tx pin
 Logic 0 = Disable pullup on the corresponding pin.
 Logic 1 = Enable pullup on the corresponding pin - Caution: Do not enable pulldown simultaneously
PIN_PULLUP_EN[11:8]: Reserved
 These bits are reserved and should remain ’0’.
3.1.1.21 PIN_PULLDOWN_EN Register Description (Read / Write)
PIN_PULLDOWN_EN[5:0]: GPI0[5:0]
Enables internal pulldown feature on the selected GPIO pins
 Logic 0 = Disable pulldown on the corresponding pin.
 Logic 1 = Enable pulldown on the corresponding pin - Caution: Do not enable pullup simultaneously
PIN_PULLDOWN_EN[6]: UART Rx
Enables internal pulldown feature on the UART Rx pin
 Logic 0 = Disable pulldown on the corresponding pin.
 Logic 1 = Enable pulldown on the corresponding pin - Caution: Do not enable pullup simultaneously
PIN_PULLDOWN_EN[7]: UART Tx
Enables internal pulldown feature on the UART Tx pin
 Logic 0 = Disable pulldown on the corresponding pin.
 Logic 1 = Enable pulldown on the corresponding pin - Caution: Do not enable pullup simultaneously
PIN_PULLDOWN_EN[11:8]: Reserved
 These bits are reserved and should remain ’0’.
3.1.1.22 LOOPBACK Register Description (Read / Write)
LOOPBACK[0]: TX_RX
When this bit is set all transmitted UART data is looped back to the UART receiver. Note that when the internal
loopback is enabled, the Tx data will be disabled and Rx data will be ignored.
 Logic 0 = Disable loopback.
 Logic 1 = Enable loopback.
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