XR21B1424_17 Datasheet, PDF (7/64 Pages) Exar Corporation – Enhanced 4-Ch Full-Speed USB UART

XR21B1424
Pin No.
Pin Name
35
GPIOB8/TXTB
36
GPIOB7/RS485B
37
GPIOB6/CLKB
38
VIO
39
GND
40
TXB
41
RXB
42
GPIOB5/RTSB#/RS485B
43
GPIOB4/CTSB#
44
GPIOB3/DTRB#
45
GPIOB2/DSRB#
46
GPIOB1/CDB#
47
GPIOB0/RIB#/RWKB#
48
GPIOD9/RXTD
49
GPIOD8/TXTD
50
GPIOD7/RS485D
51
GPIOD6/CLKD
52
TXD
53
RXD
54
GPIOD5/RTSD#/RS485D
55
GPIOD4/CTSD#
Type
I/O
I/O
I/O
PWR
PWR
O
I
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
O
I
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 19. When configured as transmit indicator, this
pin will toggle at ~10Hz intervals while the UART is transmitting data.
General purpose I/O, or auto RS-485 half-duplex control. Defaults to GPIO input with internal
pull-up resistor.
General purpose I/O, or clock or pulse output. Defaults to GPIO input with internal pull-up
resistor. See “Programmable Output Clock” on page 16.
I/O voltage input to the UART/GPIO pins. Must be between 1.8 and 3.6V. May be connected to
VCC (pin 12) if VCC_REG input voltage is 5V. See “USB Power Modes” on page 12.
Power supply common, ground.
UART Transmit Data.
UART Receive Data.
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 16 or “Multidrop mode with address matching” on page 18.
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 16.
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 17.
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 17.
General purpose I/O, or UART Carrier-Detect input (active low). Defaults to GPIO input with
internal pull-up resistor.
General purpose I/O, or UART Ring-Indicator input (active low), or Remote Wakeup input.
Defaults to GPIO input with internal pull-up resistor. Wakeup signaling to the USB host is sent
when a falling edge is detected. See “Remote Wakeup” on page 10.
General purpose I/O, or UART receive data indicator. Defaults to GPIO input with internal pull-
up resistor. See “TXT and RXT Pins” on page 19. When configured as receive indicator, this
pin will toggle at ~10Hz intervals while the UART is receiving data.
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 19. 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.
General purpose I/O, or clock or pulse output. Defaults to GPIO input with internal pull-up
resistor. See “Programmable Output Clock” on page 16.
UART Transmit Data.
UART Receive Data.
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 16 or “Multidrop mode with address matching” on page 18.
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 16.
7 / 64
exar.com/XR21B1424
Rev 1C