XR88C681CP Datasheet, PDF (88/99 Pages) Exar Corporation – CMOS DUAL CHANNEL UART (DUART)

XR88C681
Bit 7
Bit 6
Channel Mode
 J 7
 J  2' 
 J 9' 9
 J  9
Bit 5
Tx RTS
Control
 J 7
 J G%
Bit 4
CTS Enable
Tx
 J 7
 J G%
Bit 3
Bit 2
Bit 1
Stop Bit Length
Bit 0
 J 6/1
 J /6
 J /==
1 J >6
< J =1
6 J =>6
/ J 1=
> J 
= J 6/1
 J /6
J /==
* J >6

J =1
 J =>6
2 J 1=
J 
Table 30. Mode Register 2: MR2A, MR2B
Bit 7
Bit 6
Bit 5
Receiver Clock Select
 Table 9
Bit 4
Bit 3
Bit 2
Bit 1
Transmitter Clock Select
 Table 9
Table 31. Clock Select Registers: CSRA, CSRB
Bit 0
Bit 7
Bit 6
Bit 5
Miscellaneous Commands
 ! ( Section B.2
Bit 4
Bit 3
Bit 2
Enable/Disable Tx
 J 7
 -
 J 2  !
 J (% !
 J 7 $
 7 %
Table 32. Command Registers: CRA, CRB
Bit 1
Bit 0
Enable/Disable Rx
 J 7
 -
 J 2  !
 J (% !
 J 7 $
 7 %
Bit 7
Received
Break
 J 7
 J G%
Bit 6
Framing
Error
 J 7
 J G%
Bit 5
Parity Error
 J 7
 J G%
Bit 4
Overrun
Error
 J 7
 J G%
Bit 3
TXEMT
 J 7
 J G%
Bit 2
TXRDY
 J 7
 J G%
Table 33. Status Registers: SRA, SRB
Bit 1
FFULL
 J 7
 J G%
Bit 0
RXRDY
 J 7
 J G%
Bit 7
OP7
J,N>O
J5G*
Bit 6
OP6
J,N/O
J5G
Bit 5
OP5
J,N6O
J5G.
99*
Bit 4
OP4
J,N<O
J5G.
99
Bit 3
Bit 2
OP3
 J ,N1O
 J
. S 
 J 5
* 5
 J 5
* 5
Bit 1
Bit 0
OP2
 J ,NO
 J 5
/5
 J 5
5
 J 5
5
Table 34. Output Port Configuration Register: OPCR
 
==