XR17D154 Exar Corporation, XR17D154 Datasheet - Page 45

• Manufacturer Part Number: XR17D154
• Description: Four-channel Pci-bus Uart
• Manufacturer: Exar Corporation

XR17D154
UNIVERSAL (3.3V AND 5V) PCI BUS QUAD UART
REV. P1.0.0
FCTR[7:6]: TX and RX FIFO Trigger Table Select
These 2 bits select the transmit and receive FIFO trigger level table A, B, C or D. When table A, B, or C is
selected the auto RTS flow control trigger level is set to "next FIFO trigger level" for compatibility to ST16C550
and ST16C650 series. RTS/DTR# triggers on the next level of the RX FIFO trigger level, in another word, one
FIFO level above and one FIFO level below. See
6-7, i.e. if Table C is used on the receiver with RX FIFO trigger level set to 56 bytes, RTS/DTR# output will de-
asserts at 60 and re-asserts at 16.
ENHANCED FEATURE REGISTER (EFR)
Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive
character software flow control selection (see
are selected, the double 8-bit words are concatenated into two sequential characters. Caution: note that
whenever changing the TX or RX flow control bits, always reset all bits back to logic 0 (disable) before
programming a new setting.
EFR[3:0]: Software Flow Control Select
Combinations of software flow control can be selected by programming these bits (see
EFR
C
ONT
X
X
X
0
0
1
0
1
1
0
1
0
BIT
-3
-3
EFR
C
ONT
X
X
X
0
0
0
1
1
0
1
1
0
BIT
-2
-2
T
ABLE
EFR
C
ONT
17: S
X
X
X
X
0
0
1
0
1
1
1
1
BIT
-1
-1
OFTWARE
Table
EFR
Table 13
C
ONT
17). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes
0
X
X
X
X
0
0
1
1
1
1
1
F
BIT
45
LOW
-0
-0
for complete selection with FCR bit 4-5 and FCTR bit
C
No TX and RX flow control (default and reset)
No transmit flow control
Transmit Xon1/Xoff1
Transmit Xon2/Xoff2
Transmit Xon1 and Xon2/Xoff1 and Xoff2
No receive flow control
Receiver compares Xon1/Xoff1
Receiver compares Xon2/Xoff2
Transmit Xon1/ Xoff1,
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
Transmit Xon2/Xoff2,
Receiver compares Xon1 or Xon2, Xoff1 or Xoff2
Transmit Xon1 and Xon2/Xoff1 and Xoff2,
Receiver compares Xon1 and Xon2/Xoff1 and Xoff2
No transmit flow control,
Receiver compares Xon1 and Xon2/Xoff1 and Xoff2
ONTROL
T
RANSMIT AND
F
UNCTIONS
R
ECEIVE
S
OFTWARE
Table
PRELIMINARY
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17).
F
LOW
C
ONTROL