XR21B1422IL40-0A Datasheet, PDF (21/60 Pages) Exar Corporation – Enhanced 2-Ch Full-Speed USB UART

XR21B1422
Register Set Description
The internal register set of the XR21B1422 controls the UART channel functionality, basic functionality of the FIFOs, OTP
controls, as well as registers associated with the processing of driver commands. All registers are accessible via the USB
interface using the XR_SET_REG and XR_GET_REG USB commands, except for the REVISION_ID and USB_STAT reg-
isters which are accessible with the XR_GET_REVISION and XR_GET/SET_USB_STAT commands respectively. Note that
the UART_ENABLE register should be used to disable the UART prior to any register write and re-enable the UART follow-
ing any single or sequence of register writes except for the GPIO_SET, GPIO_CLEAR, TX_BREAK and ERROR_STATUS
registers.
All registers are 16 bits wide. The upper byte of single byte registers as well as bit locations with field label of ’0’ in Table 5
are reserved. All reserved bits must be written as zeroes when modifying register contents.
Address
Register Name
0x000
0x006
0x007
0x008
0x009
0x00A
0x00B
0x00C
UART_ENABLE
FLOW_CONTROL
XON_CHAR
XOFF_CHAR
ERROR_STATUS
TX_BREAK[15:8]
TX_BREAK[7:0]
XCVR_EN_DELAY
GPIO_MODE[15:8]
GPIO_MODE[7:0]
0x00D
0x00E
0x00F
0x010
0x011
GPIO_DIRECTION[15:8]
GPIO_DIRECTION[7:0]
GPIO_SET[15:8]
GPIO_SET[7:0]
GPIO_CLEAR[15:8]
GPIO_CLEAR[7:0]
GPIO_STATE[15:8]
GPIO_STATE[7:0]
GPIO_INT_MASK[15:8]
GPIO_INT_MASK[7:0]
0x012
CUSTOMIZED_INT
Table 5: XR21B1422 Register Map
Bit 7
(15)
0
0
Bit 6
(14)
0
0
Bit 5
(13)
0
0
Break
Status
Overrun
Error
Parity
Error
0
0
0
0
0
0
CLK_EN
RS485_SEL
0
GPIO7
0
GPIO7
0
GPIO7
0
GPIO7
0
GPIO7
0
GPIO6
0
GPIO6
0
GPIO6
0
GPIO6
0
GPIO6
0
GPIO5
0
GPIO5
0
GPIO5
0
GPIO5
0
GPIO5
Bit 4
(12)
Bit 3
(11)
0
0
0
Half-
Duplex
VALUE
VALUE
Framing
Error
Break
Error
VALUE (MSB)
VALUE (LSB)
0
0
XCVR
Enable
Pin
XCVR
Enable
Polarity
0
0
GPIO4 GPIO3
0
0
GPIO4 GPIO3
0
0
GPIO4 GPIO3
0
TX
GPIO4 GPIO3
0
0
GPIO4 GPIO3
0
0
0
0
0
Bit 2
(10)
0
Bit 1
(9)
RX
Bit 0
(8)
TX
Flow Control Mode Select
0
0
0
Delay
RXT_EN
TXT_EN
Mode Select
0
GPIO2
0
GPIO2
0
GPIO2
RX
GPIO2
RX
GPIO2
0
GPIO9
GPIO1
GPIO9
GPIO1
GPIO9
GPIO1
GPIO9
GPIO1
GPIO9
GPIO1
INT_
BREAK_
NEG
GPIO8
GPIO0
GPIO8
GPIO0
GPIO8
GPIO0
GPIO8
GPIO0
GPIO8
GPIO0
EN
© 2014 Exar Corporation
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Rev 1A