CD2231 Intel Corporation, CD2231 Datasheet - Page 115



Manufacturer Part Number
CD2231 Intelligent Two-channel Lan And Wan Communications Controller
Intel Corporation
Register Name: STCR
Register Description: Special Transmit Command
Default Value: x’00
Access: Byte Read/Write
Bit 7
Note: The user should not use the send XON/XOFF commands if automatic in-band flow control is
Bit 3
Bits 2:0
Special Transmit Command Register (STCR)
Async-HDLC/PPP Mode
Special characters can be transmitted preemptively (ahead of any characters in the transmit FIFO)
upon commands described below. When the special character is transmitted, the STCR is cleared
by the device.
Bit 7
Bit 6
Bits 5:4
Bit 3
Bit 2
Bit 1
enabled (Asynchronous modes only) in COR5.
Bit 6
Intelligent Two-Channel LAN and WAN Communications Controller — CD2231
For Synchronous modes, this command puts the receiver back into Syn/Flag Hunt
Clear transmitter command
This command only affects the trasmitter and is only available on Revision C and
later devices and is only effective in asynchronous protocols. It resets all transmitter
functions like a combination of clear channel, initialize channel and transmit com-
mands. ClrTx clears the transmit FIFO and clears transmit status in the CSR, except
for the TxEn bit. ClrTx clears transmit DMA buffer status in ATBSTS, BTBSTS,
and Transmit Status bits in DMABSTS. Clearing the 24312OWN bits in both the
Transmit Buffer Status registers means that DMA buffers have to be returned to the
CD2231 before transmit transfers begin again.
Reserved – must be ‘0’.
Reserved – must be ‘0’.
Transmission of the two-character sequence (7D–7E) aborts the current transmit
frame. All data in the FIFO following the abort is discarded. If DMA is used, the
remaining data up to the EOF is discarded.
Reserved – must be ‘0’.
SndSpc – Send special character command
When clear, the frame, Xon, and Xoff bits described below have no meaning.
When set, the host should also set one of the following bits: frame, Xon, or Xoff.
Frame – Send framing error
Causes the next character in the transmit stream to be sent with an incorrect Stop bit
(Stop bit is ‘0’).
This bit is intended as a test function. Unlike the Abort bit, this bit does not terminate
the transmission.
Xon – Send XON
Causes the transmission of an XON (cntl-Q or hex 11).
Bit 5
Bit 4
Bit 3
Bit 2
Motorola Hex Address: x’12
Bit 1
Intel Hex Address: x’11
Bit 0

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