XR21B1420 Datasheet, PDF (5/60 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed USB UART

XR21B1420
Pin No.
Pin Name
16
GPIO8/TXT
17
GPIO7/RS485
18
NC
19
GPIO6/CLK
20
NC
21
NC
22
NC
23
GPIO4/CTS#
24
GPIO5/RTS#/RS485
25
RX
26
TX
27
GPIO2/DSR#
28
GPIO3/DTR#
Type
I/O
I/O
-
I/O
-
-
-
I/O
I/O
I
O
I/O
I/O
Description
General purpose I/O, or UART transmit data indicator. Defaults to GPIO input with internal pull-
up resistor. See “TXT and RXT Pins” on page 15. When configured as transmit indicator, this
pin will toggle at ~10Hz intervals while the UART is transmitting data.
General purpose I/O, or RS-485 half-duplex enable output. Defaults to GPIO input with internal
pull-up resistor.
No Connect.
General purpose I/O, or clock or pulse output. Defaults to GPIO input with internal pull-up
resistor. See “Programmable Output Clock” on page 13.
No Connect.
No Connect.
No Connect.
General purpose I/O, or UART Clear-to-Send input (active low). Defaults to GPIO input with
internal pull-up resistor. See “Automatic RTS/CTS Hardware Flow Control” on page 13.
General purpose I/O, or UART Request-to-Send output (active low), or auto RS-485 half-
duplex control. Defaults to GPIO input with internal pull-up resistor. See “Automatic RTS/CTS
Hardware Flow Control” on page 13 or “Multidrop mode with address matching” on page 14.
UART Receive Data.
UART Transmit Data.
General purpose I/O, or UART Data-Set-Ready input (active low). Defaults to GPIO input with
internal pull-up resistor. See “Automatic DTR/DSR Hardware Flow Control” on page 14.
General purpose I/O, or UART Data-Terminal-Ready push-pull output (active low). Defaults to
GPIO input with internal pull-up resistor. See “Automatic DTR/DSR Hardware Flow Control” on
page 14.
Type: I = Input, O = Output, I/O = Input/Output, PWR = Power, OD = Open-Drain
© 2014 Exar Corporation
5 / 60
exar.com/XR21B1420
Rev 1A