CD2481 Datasheet, PDF (87/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

Programmable Four-Channel Communications Controller — CD2481
If the transmitter is off due to in-band flow control, the special characters will override and be sent.
Special characters will override out-of-band flow control. Also, if the transmitter is disabled, the
special character send command will override, and the character will be sent.
Table 13. SSPC[x] Settings
SSPC2
0
0
0
1
0
1
1
1
SSPC1
0
1
1
0
0
0
1
1
SSCP0
1
Send Special Character #1
0
Send Special Character #2
1
Send Special Character #3
0
Send Special Character #4
0
reserved
1
reserved
0
reserved
1
reserved
7.5.6
Special Character Recognition
Special character recognition is enabled when the SCDE bit COR3[4] is set to 1. The special
characters are programmed in the SCHR registers, and are the same characters used for the
transmitter.
If the FCT bit (COR3[5]) is set to 1, the channel process the flow control characters and discards
them. Otherwise, if FCT = 0, the received flow control characters will be processed and passed
onto the host via exception interrupt.
In the event of an error (framing and/or parity) in a received character sequence, the channel will
not interpret this character as a special character. But, if an overrun condition occurred after a
special character is detected, the new character is lost and the overrun status is set. In this
condition, the CD2481 will give both an overrun exception and a special character recognition
status.
7.5.7
Special Character Range
The Special Character Range low and high (SCRl and SCRh) registers define an inclusive range
for special character recognition in the Asynchronous mode. It may be 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 the three special character detect bits
(RISRl[6:4]. The function of the SCdet[x] bits is listed below.
Table 14. SCdet[x] Settings
SCdet2
0
0
0
SCdet1
0
0
1
SCdet0
0
No special characters/range
detected
1
Special character 1 matched
0
Special character 2 matched
Datasheet
87