XR17C154 Datasheet, PDF (40/62 Pages) Exar Corporation – 5V PCI BUS QUAD UART

XR17C154
5V PCI BUS QUAD UART
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REV. 1.3.0
TABLE 15: PARITY SELECTION
LCR BIT-5 LCR BIT-4 LCR BIT-3
PARITY SELECTION
X
X
0
No parity
0
0
1
Odd parity
0
1
1
Even parity
1
0
1
Force parity to mark, “1”
1
1
1
Forced parity to space, “0”
LCR[6]: Transmit Break Enable
When enabled the Break control bit causes a break condition to be transmitted (the TX output is forced to a
“space", LOW state). This condition remains until disabled by setting LCR bit-6 to a logic 0.
• Logic 0 = No TX break condition (default).
• Logic 1 = Forces the transmitter output (TX) to a “space”, LOW, for alerting the remote receiver of a line
break condition.
LCR[7]: Baud Rate Divisors Enable
Baud rate generator divisor (DLL/DLM) enable.
• Logic 0 = Data registers are selected (default).
• Logic 1 = Divisor latch registers are selected.
4.8.8 Modem Control Register (MCR) - Read/Write
The MCR register is used for controlling the modem interface signals or general purpose inputs/outputs.
MCR[0]: DTR# Pins
The DTR# pin may be used for automatic hardware flow control enabled by EFR bit-6 and MCR bit-2=1. If the
modem interface is not used, this output may be used for general purpose.
• Logic 0 = Force DTR# output HIGH (default).
• Logic 1 = Force DTR# output LOW.
MCR[1]: RTS# Pins
The RTS# pin may be used for automatic hardware flow control by enabled by EFR bit-6 and MCR bit-2=0. If
the modem interface is not used, this output may be used for general purpose.
• Logic 0 = Force RTS# output HIGH (default).
• Logic 1 = Force RTS# output LOW.
MCR[2]: DTR# or RTS# for Auto Flow Control
DTR# or RTS# auto hardware flow control select. This bit is in effect only when auto RTS/DTR is enabled by
EFR bit-6. DTR# selection is associated with DSR# and RTS# is with CTS#.
• Logic 0 = Uses RTS# and CTS# pins for auto hardware flow control.
• Logic 1 = Uses DTR# and DSR# pins for auto hardware flow control.
MCR[3]: (OP2)
The OP2 output is not available in the XR17C154. It is present for 16C550 compatibility during internal
loopback. See Figure 16. Logic 0 is default.
MCR[4]: Internal Loopback Enable
• Logic 0 = Disable internal loopback mode (default).
• Logic 1 = Enable internal loopback mode, see loopback section and Figure 16.
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