
CD2481
—
Programmable Four-Channel Communications Controller
126
Datasheet
1 = Characters between SCRl and SCRh (inclusive) generate special character inter-
rupts.
Bit 5
FCT
–
Flow Control Transparency mode
0 = Flow control characters received are passed to the host by receive exception
interrupts.
1 = Flow control characters received are not passed to the host.
This bit has no effect unless both TxIBE (COR2) and SCDE (COR3) are set.
Bit 4
SCDE
–
Special character detection
0 = Special character detect for SCHR1 and 2 is disabled.
1 = Special character detect for SCHR1 and 2 is enabled.
This bit must be set along with TxIBE (COR2) before FCT (COR3) becomes effec-
tive.
Bit 3
Splstp
–
Special character I-strip
When set, this bit causes the receive character to be I-stripped (bit 7 set to
‘
0
’
) for
the special character matching functions only. The character passed to the host is
unaffected. This function allows special character processing of data without know-
ing if the data is 8 bit with no parity or 7 bit with parity.
Bits 2:0
Stop2, Stop1, Stop0
–
Stop bit length
Specifies the length of the Stop bit.
COR3
–
X.21 Mode
Bit 7
Single SYN
This bit determines the number of SYN characters that need to be received before
Character Synchronization mode is considered received.
0 = Two SYN characters are required.
1 = One SYN character is required.
Note:
The SglSyn option is only available for Extended X.21 Mode; standard X.21 mode always requires
two SYN characters. When the SglSyn option is set, StrpSyn and SCDE options are disabled.
Stop2
Stop1
Stop0
Stop Bit Length
0
1
0
1 stop bit
0
1
1
1.5 stop bits
1
0
0
2 stop bits
000
–
001 and 110
–
111 are reserved.
Register Name: COR3
Register Description: Channel Option Register 3
Default Value: x
’
00
Access: Byte Read/Write
Intel Hex Address: x
’
15
Motorola Hex Address: x
’
16
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
SglSyn
SSDE
StrpSyn
SCDE
0
0
0
0