CD2401 Intel, CD2401 Datasheet - Page 70

• Manufacturer Part Number: CD2401
• Description: Multi-protocol Communications Controller
• Manufacturer: Intel

CD2401 — Multi-Protocol Communications Controller
6.2
6.2.1
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Indication (0, off) from the remote. If detected, the remainder of the current frame is discarded, and
a clear-detect indication is passed to the CPU by the RISR. However, the channel remains in
HDLC mode until modified by the CPU.
Async Processing
Data is transmitted according to the format options defined in the CORs. These options determine
the character length, parity, and Stop bit length. New data sent from the host is transmitted in a
continuous stream, unless one of the following occurs:
Transmitter In-Band Flow Control
For in-band flow control modes to be active, the Special Character Detect mode must be enabled.
Transmit in-band flow control is enabled when the TxIBE bit (COR2[6]) is set to ‘1’. When TxIBE
is set to ‘0’, in-band flow control is disabled, the IXM bit (COR2[7]) has no meaning. The XON
and XOFF characters are defined in SCHR1 and SCHR2.
When in-band flow control is enabled (TxIBE = 1) and an XOFF character is received, the channel
stops transmission after the current character in the transmit shift register; the current character in
the transmit holding register is transmitted. When IXM is set to ‘0’, transmission restarts after an
XON character is received. When IXM is set to ‘1’, transmission restarts after any character is
received.
The FCT Mode bit (COR3[5]) determines whether to pass the received flow control characters to
the host. If FCT is ‘1’, the characters are not passed to the host. If FCT is ‘0’, they are passed to the
host as exception characters. This bit does not affect non-flow control special characters.
Additional status information about transmitter in-band flow control is available in the CSR. The
TxFloff (transmit flow off) and TxFlon (transmit flow on) bits (CSR[2:1]) are used.
TxFloff = 0 is normal. TxFloff = 1 indicates that the channel has been requested by the remote to
stop transmission. This bit is reset to ‘0’ when the channel receives restart, as previously described.
This bit is reset to ‘0’ when the transmitter is enabled or disabled, or the channel is reset.
TxFlon = 0 is normal. TxFlon = 1 indicates that the channel has been requested by the remote to
restart transmission. This bit is reset to ‘0’ once the channel has restarted transmission. This bit is
reset to ‘0’ when the transmitter is enabled or disabled, or the channel is reset.
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Transmitter disabled — transmission terminated at the end of the current character until
transmitter enabled.
XOFF received from line — transmission terminated at end of the current character until XON
received or transmitter enabled.
Out-of-band flow control — transmission terminated at the end of the current character until
out-of-band flow control removed.
In-line command received in data stream from host — in-line command is executed and
transmission resumed.
Send special character command from host — the current character is completed and the
special character transmitted, after which normal transmission resumes.
Datasheet