XR16C2852_05 Datasheet, PDF (30/51 Pages) Exar Corporation – 2.97V TO 5.5V DUAL UART WITH 128-BYTE FIFOS

XR16C2852
2.97V TO 5.5V DUAL UART WITH 128-BYTE FIFOS
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REV. 2.1.1
AFR[2:1]: MF# Output Select
These bits select a signal function for output on the MF# A/B pins. These signal function are described as:
OP2#, BAUDOUT#, or RXRDY#. Only one signal function can be selected at a time.
BIT-2
0
0
1
1
BIT-1
0
1
0
1
MF# FUNCTION
OP2# (default)
BAUDOUT#
RXRDY#
Reserved
AFR[7:3]: Reserved
4.8 Modem Control Register (MCR) or General Purpose Outputs Control - Read/Write
The MCR register is used for controlling the serial/modem interface signals or general purpose inputs/outputs.
MCR[0]: DTR# Output
The DTR# pin is a modem control output. If the modem interface is not used, this output may be used as a
general purpose output.
• Logic 0 = Force DTR# output HIGH (default).
• Logic 1 = Force DTR# output LOW.
MCR[1]: RTS# Output
The RTS# pin is a modem control output and may be used for automatic hardware flow control enabled by
EFR bit-6. The RTS# output must be asserted before the auto RTS can take effect. If the modem interface is
not used, this output may be used as a general purpose output.
• Logic 0 = Force RTS# output HIGH (default).
• Logic 1 = Force RTS# output LOW. If auto RTS flow control is enabled, it will take effect after this bit has
been set.
MCR[2]: Reserved
OP1# is not available as an output pin on the 2852. But it is available for use during Internal Loopback Mode.
In the Loopback Mode, this bit is used to write the state of the modem RI# interface signal.
MCR[3]: OP2# Output / INT Output Enable
OP2# is available as an output pin on the 2852 when AFR[2:1] = ‘00’. In the Loopback Mode, MCR[3] is used
to write the state of the modem CD# interface signal. Also see pin descriptions for MF# pins.
• Logic 0 = Forces OP2# output HIGH (default).
• Logic 1 = Forces OP2# output LOW.
MCR[4]: Internal Loopback Enable
• Logic 0 = Disable loopback mode (default).
• Logic 1 = Enable local loopback mode, see loopback section and Figure 13.
MCR[5]: Xon-Any Enable
• Logic 0 = Disable Xon-Any function (for 16C550 compatibility, default).
• Logic 1 = Enable Xon-Any function. In this mode, any RX character received will resume transmit operation.
The RX character will be loaded into the RX FIFO , unless the RX character is an Xon or Xoff character and
the 2852 is programmed to use the Xon/Xoff flow control.
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