CD2481 Datasheet, PDF (151/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

Programmable Four-Channel Communications Controller — CD2481
Bit 5
Bit 4
Bit 3
Bits 2:0
Append complete (Asynchronous DMA mode only)
This bit should be set by the host when the last addition has been made to the append
buffer.
Reserved – must be zero.
Send special character(s) command
In Asynchronous mode, sends a user-defined special character or special-character
sequence. The special character is transmitted ahead of any data remaining in the
FIFO.
Special character select
SSPC2
0
0
0
0
1
1
1
1
SSCP1
0
0
1
1
0
0
1
1
SSPC0
0
1
0
1
0
1
0
1
Function
Reserved
Send Special Character 1
Send Special Character 2
Send Special Character 3
Send Special Character 4
Reserved
Reserved
Reserved
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 –Async-HDLC/PPP 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
XON
Bit 0
XOFF
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
frame. All data in the FIFO following the abort is discarded. If DMA is used, the
remaining data up to the EOF is discarded.
Bits 5:4
Reserved – must be zero.
Datasheet
151