
Programmable Four-Channel Communications Controller
—
CD2481
Datasheet
125
Bit 5
FCS preset
0 = FCS is preset to all
‘
0
’
s.
1 = FCS is preset to all
‘
1
’
s.
Bit 4
FCS mode
0 = Normal FCS mode. The CD2481 generates and appends CRC on transmit and
validates CRC on receiving, using the CRC polynomial selected through CRC Poly-
nomial Select register.
1 = Disable FCS generation and checking. The CD2481 treats the entire frame as
data.
Bit 3
Idle mode
0 = Idle in SYN.
1 = Idle in Mark.
Bit 2
Disable CRC transmission on all Bisync frames
0 = disable function
1 = CRC will not be transmitted on any frames
Bits 1:0
Pad count
–
Transmit frame leading pads
Specifies the number of pad characters to be sent when coming out of Mark Idle
mode.
COR3
–
Asynchronous Mode
Bit 7
ESCDE
–
Extended special character detect enable
0 = Special character detect for SCHR3 and SCHR4 is disabled.
1 = Special character detect for SCHR3 and SCHR4 is enabled; a special character
interrupt is generated following the receipt of a character matching SCHR3 or
SCHR4.
Bit 6
RngDE
–
Range detect enable
0 = Range detect disabled.
npad1
npad0
Number of
leading pads
0
0
0
0
1
1
1
0
2
1
1
3
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
ESCDE
RngDE
FCT
SCDE
Splstp
Stop2
Stop1
Stop0