CD2401 Intel, CD2401 Datasheet - Page 74

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

CD2401 — Multi-Protocol Communications Controller
6.2.6
6.2.7
6.2.8
74
Table 15. SCdet[x] Settings
Special Character Recognition and Range
Special character recognition is enabled when the SCDE bit (COR3[4]) is set to ‘1’. The special
characters are programmed in the SCHRs, and are the same characters used for the transmitter.
If the FCT bit (COR3[5]) is set to ‘1’, the channel processes the flow control characters and
discards them. If FCT is set to ‘0’, the received flow control characters are processed and passed
onto the host by an exception interrupt.
In the event of an error (framing and/or parity) in a received character sequence, the channel does
not interpret this character as a special character. But, if an overrun condition occurred after a
special character was detected, the new character is lost and the overrun status is set. In this
condition, the CD2401 gives both an overrun exception and a special character recognition status.
Special Character Range
The SCRs define an inclusive range for special character recognition in Asynchronous mode. This
is useful for identifying that a received character is within a certain range, such as a control
character. To disable this function, if special character detection is enabled, make both SCRl and
SCRh equal to SCHR1.
Special characters and range detection is through three special character detect bits (RISRl[6:4]).
The function of the SCdet[x] bits is listed in
UNIX Support Features
COR6 provides several functions required by UNIX TTY drivers to further reduce the amount of
character-by-character processing the CPU is required to perform. Separate receive and transmit
bits are provided to perform CR/NL (carriage return/new line) translations. In transmit, NL can be
converted to CR NL or CR converted to NL. In receive, CR can be discarded, NL converted to CR,
or CR converted to NL.
In receive processing, separate modes are provided to handle break and character error conditions.
Break conditions can be handled in the normal way (by a receive status interrupt), the condition can
be discarded, or the break can be translated to NULL (00) and passed as normal data to the CPU.
Parity and framing errors can either be handled as normal (by receive status interrupts), discarded,
translated to a NULL (00) and passed to the CPU as normal data, or the character can be passed to
the CPU as normal data preceded by the sequence FF 00.
SCdet2
0
0
0
0
1
1
SCdet1
0
0
1
1
0
1
SCdet0
0
1
0
1
0
1
No special characters and range detected.
Special character 1 matched.
Special character 2 matched.
Special character 3 matched if character 1 and 3
sequence not enabled.
Special character 4 matched if character 2 and 4
sequence not enabled.
The hex value of the receive character is within the
range: SCRl
Table
receive character
Function
15.
SCRh.
Datasheet