XR21B1420 Datasheet, PDF (54/60 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed USB UART

XR21B1420
PIN_CFG_DSR (0x02D) - Read/Write OTP
This register configures the functionality of the GPIO2/DSR pin
Bit
7
6
5:2
1:0
Default
Description
0
PULLUP_EN
This register bit is used to enable the internal pull-up resistor. This setting will be ignored if GPIO3/DTR# is con-
figured as an output.
0: Do not enable internal pull-up
1: Enable internal pull-up if configured as an input
0
PULLDOWN_EN
This register bit is used to enable the internal pull-down resistor. This setting will be ignored if GPIO3/DTR# is
configured as an output.
0: Do not enable internal pull-down
1: Enable internal pull-down if configured as an input (will not be enabled if Pull up is enabled)
0
RESERVED
These bits are reserved and should be written as ’0’.
0
CTRL
00: GPIO2/DSR# is configured as a GPIO input
01: GPIO2/DSR# is configured as a GPIO open drain output
10: GPIO2/DSR# is configured as a GPIO push-pull output
11 to 111: Invalid, do not use
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
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Rev 1A