XR22801 Datasheet, PDF (26/42 Pages) Exar Corporation – Hi-Speed USB to 10/100 Ethernet Bridge

XR22801
PIN_PULLDOWN_EN (0x055) - Read/Write
Bit
15:10
7
6
5:0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
UART TX
0: Disable internal pull-down resistor on the UART TX pin
1: Enable internal pull-down resistor on the UART TX pin. (Will not be enabled if pull-up is already enabled.)
0
UART RX
0: Disable internal pull-down resistor on the UART RX pin
1: Enable internal pull-down resistor on the UART RX pin. (Will not be enabled if pull-up is already enabled.)
0
GPIO[N]
0: Disable internal pull-down resistor on the corresponding GPIO[N] pin
1: Enable internal pull-down resistor on the corresponding GPIO[N] pin. (Will not be enabled if pull-up is
already enabled.)
LOOPBACK (0x056) - Read/Write
Bit
15:3
2
1
0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
DTR_DSR
0: Disable DTR to DSR internal loopback
1: Enable DTR to DSR internal loopback
0
RTS_CTS
0: Disable RTS to CTS internal loopback
1: Enable RTS to CTS internal 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.
0: Disable TX to RX internal loopback
1: Enable TX to RX internal loopback
IR_MODE (0x057) - Read/Write
Bit
15:3
2
1
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
TX_Pulse
0: TX pulse width is 3/16 of the bit period
1: TX pulse width is 4/16 of the bit period
0
RX_Invert
0: RX input is not inverted before sampling
1: RX input is inverted before sampling
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Rev 1B