XR20M1280
46
I2C/SPI UART WITH 128-BYTE FIFO AND INTEGRATED LEVEL SHIFTERS
REV. 1.0.0
FCTR[3]: Auto RS-485 Direction Control
Logic 0 = Standard ST16C550 mode. Transmitter generates an interrupt when transmit holding register
becomes empty and transmit shift register is shifting data out.
Logic 1 = Enable Auto RS485 Direction Control function. The direction control signal, RTS# pin, changes its
output logic state from LOW to HIGH one bit time after the last stop bit of the last character is shifted out.
Also, the Transmit interrupt generation is delayed until the transmitter shift register becomes empty. The
RTS# output pin will automatically return to a LOW when a data byte is loaded into the TX FIFO. However,
RTS# behavior can be inverted by setting EMSR[3] = 1.
FCTR[5:4]: Transmit/Receive Trigger Table Select
See
TABLE 19: TRIGGER TABLE SELECT
BIT-5
BIT-4
TABLE
0
Table-A (TX/RX)
0
1
Table-B (TX/RX)
1
0
Table-C (TX/RX)
1
Table-D (TX/RX)
FCTR[6]: Scratchpad Swap
Logic 0 = Scratch Pad register is selected as general read and write register. ST16C550 compatible mode.
Logic 1 = FIFO Count register (Read-Only), Enhanced Mode Select Register (Write-Only). Number of
characters in transmit or receive FIFO can be read via scratch pad register when this bit is set. Enhanced
Mode Select Register is selected when it is written into.
FCTR[7]: Programmable Trigger Register Select
Logic 0 = Registers TRG and FC selected for RX.
Logic 1 = Registers TRG and FC selected for TX.
3.19
Enhanced Feature Register (EFR) - Read/Write
Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive
character software flow control selection (see Table 20). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes
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.
FCTR