XR21V1412IL-0A Datasheet, PDF (24/32 Pages) Exar Corporation – 2-CH FULL-SPEED USB UART

XR21V1412
2-CH FULL-SPEED USB UART
REV. 1.3.0
3.3.11 RS485_DELAY Register Description (Read/Write)
RS485_DELAY[3:0]: Turn-around delay
This is the number of bit times the V1412 waits before de-asserting the GPIO5/RTS#/RS485 pin when it is
configured for automatic RS-485 half-duplex control.
RS485_DELAY[7:4]: Reserved
These bits are reserved and should be ’0’.
3.3.12 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 1.5, UART” on
page 9.
TABLE 14: 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[7:4]: 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.
3.3.13 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[7:6]: Reserved
These register bits are reserved and should be ’0’.
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