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XR21B1424_17 Datasheet, PDF (59/64 Pages) Exar Corporation – Enhanced 4-Ch Full-Speed USB UART
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PIN_CFG_DATA_PINS (0x02E) - Read/Write OTP
This register configures the functionality of the RX and TX data pins
Bit
7
6
5
4:1
0
Default
Description
0
RX_PULLUP_EN
This register bit is used to enabled the internal pull-up on the RX pin
0: Do not enable internal pull-up on RX pin
1: Enable internal pull-up on RX pin
0
RX_PULLDOWN_EN
This register bit is used to enabled the internal pull-down on the RX pin
0: Do not enable internal pull-down on RX pin
1: Enable internal pull-down on RX pin (will not be enabled if pull-up is enabled)
0
RX_REMOTE_WAKE_EN
This register bit enables remote wakeup capability on the RX pin
0: RX pin is not enabled for remote wakeup
1: RX pin is enabled for remote wakeup if global remote wakeup is enabled
0
RESERVED
These bits are reserved and should be written as ’0’.
0
TX_CTRL
0: TX open drain output
1: TX push-pull output
XR21B1424
SUSPEND_STATE_MSB (0x02F) - Read/Write OTP
This register configures the state of the GPIO pins during suspend state. Note that RX and TX data pins are not controlled
by SUSPEND_STATE. USE_SUSPEND is not a physical pin, but instead acts as the control for pins in the suspended state
and is in the most significant bit position of SUSPEND_MODE_MSB.
Bit
7
6
5:4
3
2
1
0
Default
Description
0
GPIO9/RXT
0: Corresponding bit set to logic ’0’ during suspend if USE_SUSPEND = ’1’
1: Corresponding bit set to logic ’1’ during suspend if USE_SUSPEND = ’1’
0
GPIO8/TXT
0: Corresponding bit set to logic ’0’ during suspend if USE_SUSPEND = ’1’
1: Corresponding bit set to logic ’1’ during suspend if USE_SUSPEND = ’1’
0
Not used
0
GPIO7/RS485
0: Corresponding bit set to logic ’0’ during suspend if USE_SUSPEND = ’1’
1: Corresponding bit set to logic ’1’ during suspend if USE_SUSPEND = ’1’
0
GPIO4/CTS#
0: Corresponding bit set to logic ’0’ during suspend if USE_SUSPEND = ’1’
1: Corresponding bit set to logic ’1’ during suspend if USE_SUSPEND = ’1’
0
GPIO5/RTS#/RS485
0: Corresponding bit set to logic ’0’ during suspend if USE_SUSPEND = ’1’
1: Corresponding bit set to logic ’1’ during suspend if USE_SUSPEND = ’1’
0
GPIO6/CLK
0: Corresponding bit set to logic ’0’ during suspend if USE_SUSPEND = ’1’
1: Corresponding bit set to logic ’1’ during suspend if USE_SUSPEND = ’1’
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exar.com/XR21B1424
Rev 1C
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