xr21b1411 Exar Corporation, xr21b1411 Datasheet - Page 15

• Manufacturer Part Number: xr21b1411
• Description: Enhanced 1-ch Full-speed Usb Uart
• Manufacturer: Exar Corporation

REV. 1.1.0
These registers select the flow control mode. These registers should only be written to when the UART is
disabled.
behavior.
FLOW_CONTROL[2:0]: Flow control mode select
FLOW_CONTROL[3]: Half-Duplex Mode
FLOW_CONTROL[11:4]: Reserved
These bits are reserved and should remain ’0’.
The XON_CHAR stores the XON character that is used in the Automatic Software Flow control.
XON_CHAR[7:0]: XON Character
In Automatic Software Flow control mode, the UART will resume data transmission when the XON character
has been received.
For behavior in the Address Match mode, see
page
XON_CHAR[11:8]: Reserved
These bits are reserved and should remain ’0’.
The XOFF_CHAR stores the XOFF character that is used in the Automatic Software Flow control.
XOFF_CHAR[7:0]: XOFF Character
In Automatic Software Flow control mode, the UART will suspend data transmission when the XOFF character
has been received.
For behavior in the Address Match mode, see
page
XOFF_CHAR[11:8]: Reserved
These bits are reserved and should remain ’0’.
3.1.1.7
3.1.1.8
3.1.1.9
Logic 0 = Normal (full-duplex) mode. The UART can transmit and receive data at the same time.
Logic 1 = Half-duplex Mode. In half-duplex mode, any data on the RX pin is ignored when the UART is
transmitting data.
8.
8.
M
ODE
0
1
2
3
4
Writing to the FLOW_CONTROL register when the UART is enabled will result in undefined
FLOW_CONTROL Register Description (Read / Write)
XON_CHAR Register Description (Read / Write - Default 0x17)
XOFF_CHAR Register Description (Read / Write - Default 0x19)
B
IT
0
0
0
0
1
-2 B
IT
0
0
1
1
0
-1 B
IT
0
1
0
1
0
-0
T
ABLE
No flow control, no address matching.
HW flow control enabled. Auto RTS/CTS or DTR/DSR must be selected by
GPIO_MODE.
SW flow control enabled
Multidrop mode - RX only after address match, TX independent. (Typically
used with GPIO_MODE 3)
Multidrop mode - RX / TX only after address match. (Typically used with
GPIO_MODE 4)
6: F
LOW
“Section 1.3.5, Multidrop mode with address matching” on
“Section 1.3.5, Multidrop mode with address matching” on
C
ONTROL
15
M
ODE
M
ENHANCED 1-CH FULL-SPEED USB UART
ODE
S
ELECTION
D
ESCRIPTION
XR21B1411