CD2481 Datasheet, PDF (121/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

Programmable Four-Channel Communications Controller — CD2481
Bit 7
Bit 6
Bits 5:4
Bit 3
Bit 2
Bit 1
Bit 0
IXM – Implied XON mode
IXM has meaning only when TxIBE is set.
If transmission has been stopped due to a received XOFF character, and:
If IXM = 0, transmission is resumed only after the receipt of an XON character or a
transmit enable command by the CCR (Channel Command register).
If IXM = 1, transmission is resumed after the receipt of any character or a transmit
enable command by the CCR.
TxIBE – Transmit in-band flow control enable
If TxIBE is clear, there is no in-band flow control.
If TxIBE is set, transmission is stopped after the receipt of an XOFF character (cntl-
S or hex 13). Immediately after receiving an XOFF, any character in the Transmit
Shift register or Holding register is transmitted, and then character transmission is
halted. Thus, no more than two characters are sent after receiving an XOFF.
Depending on the IXM bit, either the receipt of an XON (cntl-Q or hex 11) character
or any other character (IXM = 1) restarts the transmission. A transmit enable com-
mand by the CCR also restarts the transmission.
Reserved – must be zero.
RLM – Remote loop back
RLM = 1, enables Remote Loopback mode
RLM = 0, disables Remote Loopback mode
RtsAO – RTS automatic output enable
If RtsAO = 1, the RTS* output pin remains enabled during DMA or character bursts
from the transmit FIFO. If the CTS* input pin goes high, RTS* goes high and trans-
mission is stopped after the current burst is completed.
CtsAE – CTS automatic enable
When clear, the transmitter output enable is independent of the CTS* input pin.
When set, the CTS* input pin is evaluated prior to the transmission of each character.
If CTS* is asserted low, that character is transmitted completely. If CTS* is high,
that character transmission is held until CTS* goes low.
DsrAE – DSR automatic enable
When clear, the receiver input enable is independent of the DSR* input pin.
When set, the DSR* input pin is evaluated at the end of each received character. If
DSR* is asserted low, the receiver input is enabled for the next character. If DSR*
is high, the receiver is disabled until DSR* goes low.
Datasheet
121