XR21B1411IL-0A-EB Datasheet, PDF (18/30 Pages) Exar Corporation – ENHANCED 1-CH FULL-SPEED USB UART

XR21B1411
ENHANCED 1-CH FULL-SPEED USB UART
REV. 1.2.0
RS485_DELAY[11:4]: Reserved
These bits are reserved and should be ’0’.
3.1.1.13 GPIO_MODE Register Description (Read / Write)
GPIO_MODE[2:0]: GPIO Mode Select
There are 4 modes of operation for the GPIOs. The descriptions can be found in “Section 1.3, UART” on
page 5.
TABLE 7: GPIO MODES
BITS
[2:0]
GPIO0 GPIO1
GPIO2
GPIO3
GPIO4
GPIO5
MODE DESCRIPTION
000 GPIO0 GPIO1 GPIO2 GPIO3 GPIO4 GPIO5 GPIO Mode, All GPIO pins available as GPIO
001 GPIO0 GPIO1 GPIO2 GPIO3 CTS#
RTS# GPIO4 and GPIO5 used for Auto RTS/CTS HW
Flow Control
010 GPIO0 GPIO1 DSR#
DTR#
GPIO4 GPIO5 GPIO2 and GPIO3 used for Auto DTR/DSR HW
Flow Control
011 GPIO0 GPIO1 GPIO2 GPIO3 GPIO4 RS485 GPIO5 used for auto RS-485 half-duplex control
100 GPIO0 GPIO1 GPIO2 GPIO3 GPIO4 RS485 GPIO5 used for auto RS-485 half-duplex control
after address match (See FLOW_CONTROL
mode 4).
GPIO_MODE[3]: RS485 Polarity
 Logic 0 = GPIO5/RTS#/RS485 Low for TX
 Logic 1 = GPIO5/RTS#/RS485 High for TX
GPIO_MODE[11:4]: Reserved
These register bits are reserved. When writing to these bits, the value should be ’0’. When reading from these
bits, they are undefined and should be ignored.
3.1.1.14 GPIO_DIRECTION Register Description (Read / Write)
This register controls the direction of pins configured as GPIO. (Pins configured for UART functions via the
GPIO_MODE register, e.g. RTS# are not controlled or reported in the GPIO_DIRECTION register.)
GPIO_DIRECTION[5:0]: GPIOx Direction
 Logic 0 = GPIOx is an input.
 Logic 1 = GPIOx is an output.
GPIO_DIRECTION[11:6]: Reserved
These register bits are reserved and should be ’0’.
3.1.1.15 GPIO_SET Register Description (Read / Write)
Writing a ’1’ in this register sets the corresponding GPIO output high. Writing a ’0’ in this register sets the
corresponding GPIO output low. For GPIO pins configured as an input via the GPIO_DIRECTION register this
register has no effect. Bits 11-6 are unused and should be ’0’.
3.1.1.16 GPIO_CLEAR Register Description (Read / Write)
Writing a ’1’ in this register clears the corresponding GPIO output low. Writing a ’0’ to a bit has no effect. Bits
11-6 are unused and should be ’0’.
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