CD2481 Datasheet, PDF (152/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

CD2481 — Programmable Four-Channel Communications Controller
Bit 3
sndsp – 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.
Bit 2
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.
Bit 1
XON – Send XON
Causes the transmission of an XON (cntl-Q or hex 11).
Note: The user should not use the send XON/XOFF commands if automatic in-band flow control is
enabled (Asynchronous modes only) in COR5.
Bit 0
XOFF – Send XOFF
Causes the transmission of an XOFF (cntl-S or hex 13).
The command structure associated with the sndsp Control bit is:
sndsp
0
1
1
1
frame
X
1
0
0
XON
X
X
1
0
XOFF
X
X
X
1
Action
Send Special Disabled
Send one character with FE
Send XON
Send XOFF
Note: The user should not use the send XON/XOFF commands if automatic in-band flow control is
enabled (Asynchronous modes only) in COR5.
STCR –SLIP/MNP4 Mode
Register Name: STCR
Register Description: Special Transmit Command Register
Default Value: x’00
Access: Byte Read/Write
Bit 7
Bit 6
Bit 5
Bit 4
0
AbortTx
0
0
Bit 3
SndSpc
Intel Hex Address: x’11
Motorola Hex Address: x’12
Bit 2
Frame
Bit 1
0
Bit 0
0
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
Reserved – must be zero.
Bit 6
Abort
Transmission of the two-character sequence (7D–7E) aborts the current transmit
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Datasheet