XR21B1420IL28-0A Datasheet, PDF (34/60 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed USB UART

XR21B1420
RX_THRESHOLD (0x047) - Read/Write
This register sets the threshold for asserting flow control when enabled in the UART. This register applies to both hardware
and software flow control.
Bit
15:10
9:0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0x1C2
Count
Hardware or software flow control is asserted when the RX_FIFO reaches the threshold count set in this regis-
ter. Default value for this register is 450 or 0x1C2.
CUSTOM_DRIVER (0x060) - Write Only
This register determines which device driver is used (custom or CDC driver). For proper operation, a custom driver must set
the ACTIVE bit prior to sending any of the 4 CDC_ACM commands supported by the XR21B1420.
Bit
15:1
0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
Active
0: Informs the XR21B1420 that the standard CDC_ACM driver is being used.
1: Informs the XR21B1420 that a custom driver is being used.
SUSPEND_STATE (0x6A) - Read/Write
This register is used to set the state of GPIO pins based on the setting of the USE_SUSPEND bit in the SUSPEND_MODE
register.
Bit
15:14
13
12
11
10
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
DSR
0: When USE_SUSPEND is ’1’, clear this bit to a ’0’
1: When USE_SUSPEND is ’1’, set this bit to a ’1’
0
DTR
0: When USE_SUSPEND is ’1’, clear this bit to a ’0’
1: When USE_SUSPEND is ’1’, set this bit to a ’1’
0
RI
0: When USE_SUSPEND is ’1’, clear this bit to a ’0’
1: When USE_SUSPEND is ’1’, set this bit to a ’1’’
0
CD
0: When USE_SUSPEND is ’1’, clear this bit to a ’0’
1: When USE_SUSPEND is ’1’, set this bit to a ’1’’
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Rev 1A