CD2231 Intel Corporation, CD2231 Datasheet - Page 75

• Manufacturer Part Number: CD2231
• Description: CD2231 Intelligent Two-channel Lan And Wan Communications Controller
• Manufacturer: Intel Corporation

6.5
6.5.1
Datasheet
SOH
Figure 18. ARAP 2.0 Frame
Start Flag
ESC
NOTE: The DLE (ARAP 1.0) and ESC (ARAP 2.0) characters in the middle of the data stream, indicated by the
Async Processing
Data is transmitted according to the format options defined in the Channel Option registers. 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 (Transmit In-Band Enable) bit
(COR2[6]) is set to ‘1’. When TxIBE is set to ‘0’, in-band flow control is disabled, the IXM
(Implied XON Mode) bit, also in COR2[7], has no meaning. The XON and XOFF characters are
defined in the Special Character registers SCHR[1] and SCHR[2].
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 and the current
character in the Transmit Holding register are transmitted. When IXM = 0, transmission restarts
after an XON character is received. When IXM = 1, transmission restarts after any character is
received.
The FCT (flow control transparency) Mode bit (COR3[5]) determines whether to pass the received
flow control characters to the host. If FCT = 1, the characters are not passed to the host. If FCT = 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
(Channel Status register). The TxFloff (Transmit Flow Off) and TxFlon (Transmit Flow On) bits
CSR[2:1] are used.
•
•
•
•
•
STX
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 is transmitted after which normal transmission is resumed.
Intelligent Two-Channel LAN and WAN Communications Controller — CD2231
‘T’ column, are inserted for transparency and thus not included in the FCS calculation.
data
data
DLE
DLE
T
data
data
ESC
End Flag
ETX
FCS1
FCS2
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