CD2481 Datasheet, PDF (100/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

CD2481 — Programmable Four-Channel Communications Controller
Since the channel does not look for an end of frame delimiter, the host must determine when to end
the frame and/or to terminate the buffer (if DMA is used) via software. It also must detect when to
start another frame.
Extended-X.21 mode keeps passing received data to host before and/or after it has received the
SYN character(s). The host can discard all the junk characters before SYN character(s) whenever
the chip detects the SYN character(s) and generates an interrupt.
If the SSDE bit COR3[4] is not set, Extended X.21 mode does not strip SYN characters and special
characters from the incoming data stream.
Note: Strip SYN and SCDE are functional only if SSDE is set.
Example 1: (Two Syn mode)
Incoming data:
Junk Junk SYN SYN Data Data Data Data Data Data Data Data
Note: a SYN character detect interrupt is generated after the second SYN.
Data passed to the host:
Junk Junk SYN SYN Data Data Data Data Data Data Data Data
Example 2: (Single Syn mode)
Incoming data:
Junk Junk SYN Data Data Data Data Data Data Data Data
Note: a SYN character detect interrupt is generated after the SYN.
Data passed to the host:
Junk Junk SYN Data Data Data Data Data Data Data Data
7.9
Programmable Sync
Programmable Sync mode provides a means to enable the CD2481 to be configured for use in
many non-standard character or byte synchronous applications. The protocol can be used in data
streams that consist of 5, 6, 7 or 8-bit “characters” and can be enabled to synchronize to the data
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Datasheet