SCD1284 INTEL [Intel Corporation], SCD1284 Datasheet - Page 63

• Manufacturer Part Number: SCD1284
• Description: IEEE 1284-Compatible Parallel Interface Controller with Two High-Speed Asynchronous Serial Ports
• Manufacturer: INTEL [Intel Corporation]

IEEE 1284-Compatible Parallel Interface Controller — CD1284
5.7.2
Non-UNIX Receive Special Character Processing
In addition to UNIX special-character processing, the CD1284 provides other special character
recognition capabilities. The CD1284 has four registers that define special characters, SCHR1–
SCHR4. SCHR1 and SCHR2, are used in flow-control activities and (see
Section
5.6). SCHR3 and
SCHR4 define two additional special characters that the CD1284 can scan for in the receive data
stream. Recognition of special characters 3 and 4 are enabled by the SCD34 bit (COR3[6]). If
either of these characters are received, a special character detect (receive exception) service request
is sent. Note that if automatic in-band flow control is not enabled, SCHR1 and SCHR2 can still be
used as special characters. They are detected and reported as receive exceptions, but they do not
cause flow-control activities to be envoked.
The range detect function is another special character function. If this mode is enabled (COR3[7]
set), the CD1284 compares all received characters against the values in the SCRL and SCRH
registers. If the character received falls between these two values (inclusive), a special character
detect service request is posted.
The status shown in the RDSR indicates which of the special character recognition conditions were
met and caused the receive exception service request.
Datasheet
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