CD1865 datasheet(63/150 Pages) INTEL

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Intelligent Eight-Channel Communications Controller — CD1865

Datasheet

The user may individually enable any CD1865 channel to recognize special characters. There are

six bits used to control the various recognition and flow-control modes.

The following four registers are used to control character recognition:

The following table shows the effects of XonCH and XoffCH:

Note:

The two-character pairs can share a common first character; however, the same character must be

programmed in both SCHR1 and SCHR2.

Single- versus double-character recognition is controlled by XonCH and XoffCH. If single-

character compare is enabled, the CD1865 compares data in the data stream against the four special

characters stored in the Special Character registers (SCHR1-4). If fewer than four special

characters are required, the unused Special Character register(s) should be disabled by duplicating

the pattern to be matched in the unneeded register. When reporting a special character, the CD1865

always reports the lowest-number Special Character register that matches.

To set up Special Character Recognition, first set the characters to be matched in registers SCHR1-

4, then set XonCH and XoffCH according to the length of match wanted. Set the SCDE bit, and

lastly enable service requests by setting RxSC.

Special characters are reported to the host by placing the appropriate status word in the Status FIFO

and the recognized special character in the Receive Data FIFO. In the case of a two-character

sequence, only the second character is stored in the Receive FIFO. This is because there is room

only for one character and preserving both is not needed as these characters are user-defined.

7.1.9

Flow-Control Characters

Automatic In-Band Flow Control of the CD1865 transmitter is a subset of the Special Character

Recognition capability, so to understand both these features is important. Refer to Section 7.2 on

page 68 for transmitter operation. Flow-control characters and operation are programmable on a

per-channel basis. This is important to operating systems that allow users to configure their own

terminal settings independently.

Bit Name

Function

SCDE

COR3

Enables detection of special characters. Must be set for In-Band Flow

Control to work.

RxSC

Enables generation of service requests. Cannot be overridden by

other bits. Does not need to be set for In-Band Flow Control to work.

XonCH

COR3

Controls single- versus double-character matching.

XoffCH

COR3

Controls single- versus double-character matching.

XonCH

XoffCH

Characters matched

Match on: any of SCHR1–4

Match on: SCHR1 or SCHR3 or (SCHR2 and SCHR4)

Match on: (SCHR1 and SCHR3) or SCHR2 or SCHR4

Match on: (SCHR1 and SCHR3) or (SCHR2 and SCHR4)

CD1865 Datasheet(PDF) 63 Page - Intel Corporation

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