XR16C2850
hardware flow control. -RTS functions normally when
hardware flow control is disabled.
FCTR BIT-3:
Interrupt type select and Auto RS-485 half duplex
control.
0 = Automatic RTS flow control is disabled (normal
default condition).
1 = Enable Automatic RTS flow control.
0=StandardST16C550mode.Transmittergenerates
interrupt when transmit holding register is empty and
transmit shift register is shifting data out.
1 = Transmit empty interrupt. Transmit interrupt is
generated when the transmitter holding and shift
register is empty. The -RTS A/B out pins will stay high
during receive mode and will go low during transmit
mode.
EFR bit-7:
Automatic CTS Flow Control.
Logic 0 = Automatic CTS flow control is disabled
(normal default condition).
Logic 1 = Enable Automatic CTS flow control. Trans-
mission will stop when -CTS goes to a logic 1. Trans-
mission will resume when the -CTS pin returns to a
logic 0.
FCTR BIT 4-5:
Transmit / receive trigger table select.
FEATURE CONTROL REGISTER
This register controls the XR16C2850 new functions
that are not available on ST16C550 or ST16C650.
FCTR
Bit-5
FCTR
Bit-4
Table
0
0
1
1
0
1
0
1
Table-A (TX/RX)
Table-B (TX/RX)
Table-C (TX/RX)
Table-D (TX/RX)
FCTR BIT 0-1:
User selectable -RTS hysterisis for hardware flow
control application. After reset, these bits are set to 0
to select the next trigger level for hardware flow
control.
FCTR BIT-6:
Register mode select.
FCTR
Bit-1
FCTR
Bit-0
Trigger
level
0 = Scratch Pad register is selected as general read
and write register (ST16C550 compatible mode).
1 = FIFO count register. Number of characters in
transmit or receive holding register can be read via
scratch pad register when this bit is set.
0
0
Next trigger
level
0
1
1
1
0
1
4 word+trigger level
6 word+trigger level
8 word+trigger level
FCTR BIT-7:
Programmable trigger register select.
0 = Receiver programmable trigger level register is
selected.
FCTR BIT-2:
0 = Select RX input as encoded IrDa data.
1 = Transmitter programmable trigger level register is
selected.
1 = Select RX input as active high encoded IrDa data.
Rev. 1.00P
27
EXAR [ EXAR CORPORATION ]
