XR21B1424_17 Datasheet, PDF (28/64 Pages) Exar Corporation – Enhanced 4-Ch Full-Speed USB UART

XR21B1424
GPIO_MODE (0x00C) - Read/Write
Bit
15:10
9
8
7
6:5
4
3
2:0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
1
Receive Toggle
0: GPIO9 is used for general purpose I/O
1: GPIO9 is used to receive toggle output (default).
1
Transmit Toggle
0: GPIO8 is used for general purpose I/O.
1: GPIO8 is used to transmit toggle output (default).
0
Clock Enable
0: GPIO6 is used for general purpose I/O
1: GPIO6 is used to output a clock. See “OUTCLK (0x018) - Read/Write” on page 35.
0
Auto RS-485 Half-Duplex Select
00: GPIO. GPIO7/RS485 is used for general purpose I/O
01: RS485_EN_ACT. GPIO7/RS485 is used for auto RS-485 half-duplex enable. Asserted whenever the UART is transmitting
10: RS485_EN_FLOW. GPIO7/RS485 is used for auto RS-485 half-duplex enable. Asserted for the duration of the address
match
11: RESERVED. Reserved value, do not use
0
Auto RS-485 Half-Duplex Pin
0: GPIO5/RTS#/RS485 function is selected by GPIO_MODE[2:0]. GPIO7/RS485 function is GPIO.
1: GPIO7/RS485 function is selected by GPIO_MODE[6:5]. GPIO5/RTS#/RS485 function must be any function other than
that selected for GPIO7/RS485.
0
Auto RS-485 Half-Duplex Polarity
0: Active low auto. RS-485 half-duplex enable
1: Active high auto. RS-485 half-duplex enable
0
GPIO Mode Select
000: GPIO. RTS/CTS and DTR/DSR are used for general purpose I/O.
001: RTS_CTS. GPIO4 and GPIO5 used for Auto RTS/CTS HW Flow Control
010: DTR_DSR. GPIO2 and GPIO3 used for Auto DTR/DSR HW Flow Control
011: RS485_EN_ACT. GPIO5/RTS#/RS485 pin used for auto .RS-485 half-duplex enable during Transmit
100: RS485_EN_FLOW. GPIO5/RTS#/RS485 pin used for auto RS-485 half-duplex enable after address match.
101 to 111: Reserved. Reserved value, do not use.
GPIO_DIRECTION (0x00D) - Read/Write
This register controls the direction of pins that are configured as GPIO. Pins that are configured for alternate functions via
the GPIO_MODE register are not controlled by this register.
Bit
15:10
9:0
Default
0
Reserved
These bits are reserved and should be ‘0.’
0
GPIO Direction of GPIO[9:0]
0: GPIOx is an input.
1: GPIOx is an output.
Description
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exar.com/XR21B1424
Rev 1C