CD2481 Datasheet, PDF (118/222 Pages) Intel Corporation – Programmable Four-Channel Communications Controller

CD2481 — Programmable Four-Channel Communications Controller
Bit 3
NoStrip
0 = NoStrip disabled; stripping of DLE-SYN or SYN-SYN will occur.
1 = NoStrip enabled; if this bit is set, stripping of DLE-SYN (transparent frames) or
SYN-SYN (non-transparent frames) is disabled. DLE-SYN or SYN-SYN will be
kept in the frame data.
Bit 2
Alternate Control
Alt–Ctrl has significance only if COR2 bit 7 (LRC) is 0 (which selects CRC-16), and
COR2 bit 5 is 1, which allows the 7 bit ASCII data in 8 bit EBCDIC format. The
eighth bit is for error-checking, while for transparent case, the host should use CRC–
16 for error checking. In all cases the CD2481 would use CRC–16 calculation and
checking. The burden of checking character validity (through VRC or CRC–16 dur-
ing reception) along with 8th bit parity addition (during transmission) is to be burned
by host alone.
Note: As a side effect, the CRC error bit (set by CD2481) may not be valid for the host. It may be ignored
in case of non-transparent text and may be used in case of transparent text.
Bits 1:0
Extra SYN characters
This field determines the number of extra synchronize (SYN) characters that are
transmitted before a frame is started. The two required SYNs are not included in this
count. This is a binary encode field in which the two required SYNs are followed by
the encoded number of characters (00 = no extra characters; 11 = 3 extra characters)
Note: In ASCII mode, data is 7 bit with LRC (odd parity) checking only. In EBCDIC mode, data is 8 bit
with CRC checking only. See exception under Alternate Control Bit (COR2 bit 2).
COR2 – Asynchronous
Register Name: COR2
Register Description: Channel Option Register 2
Default Value: x’00
Access: Byte Read/Write
Bit 7
Bit 6
Bit 5
Bit 4
IXM
TxIBE
ETC
0
Bit 3
RLM
Intel Hex Address: x’14
Motorola Hex Address: x’17
Bit 2
RtsAO
Bit 1
CtsAE
Bit 0
DsrAE
Bit 7
IXM – Implied XON mode
IXM has meaning only when TxIBE is set.
If transmission has been stopped due to a received XOFF character, then:
If IXM = 0, then transmission is resumed only after the receipt of an XON character
or a transmit enable command by the Channel Command register (CCR).
If IXM = 1, then transmission is resumed after the receipt of any character or a trans-
mit enable command by the CCR.
Bit 6
TxIBE – Transmit in-band flow control enable
If TxIBE is clear, there is no in-band flow control.
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Datasheet