XR17D154 Exar Corporation, XR17D154 Datasheet - Page 44

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

áç
áç
PRELIMINARY
FCTR [3:0] - Auto RTS/DTR Flow Control Hysteresis Select
These bits select the auto RTS/DTR flow control hysteresis and only valid when TX and RX Trigger Table-D is
selected (FCTR bit-6 and 7 are set to logic 1). The RTS/DTR hysteresis is referenced to the RX FIFO trigger
level. After reset, these bits are set to logic 0 selecting the next FIFO trigger level for hardware flow control.
Table 16
FCTR[4]: Infrared RX Input Logic Select
FCTR[5]: Auto RS485 Enable
Auto RS485 half duplex control enable/disable.
áç
áç
Logic 0 = Select RX input as active high encoded IrDA data, normal, (default).
Logic 1 = Select RX input as active low encoded IrDA data, inverted.
Logic 0 = Standard ST16C550 mode. Transmitter generates an interrupt when transmit holding register
(THR) becomes empty. Transmit Shift Register (TSR) may still be shifting data bit out.
Logic 1 = Enable Auto RS485 half duplex direction control. RTS# output changes its logic level from 1 to 0
when finished sending the last stop bit of the last character out of the TSR register. It changes back to logic
level 1 from 0 when a data byte is loaded into the THR or transmit FIFO. The change to logic 1 occurs prior
sending the start-bit. It also changes the transmitter interrupt from transmit holding to transmit shift register
(TSR) empty.
below shows the 16 selectable hysteresis levels.
T
ABLE
FCTR B
16: 16 S
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
IT
-3 FCTR B
ELECTABLE
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
IT
-2 FCTR B
H
YSTERESIS
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
IT
-1 FCTR B
L
EVELS
44
UNIVERSAL (3.3V AND 5V) PCI BUS QUAD UART
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
W
IT
HEN
-0
T
RIGGER
RTS/DTR H
(
CHARACTERS
T
ABLE
+/- 16
+/- 24
+/- 32
+/- 12
+/- 20
+/- 28
+/- 36
+/- 40
+/- 44
+/- 48
+/- 52
+/- 4
+/- 6
+/- 8
+/- 8
0
YSTERESIS
-D
IS
)
S
ELECTED
XR17D154
REV. P1.0.0