
CD2481
—
Programmable Four-Channel Communications Controller
124
Datasheet
Bit 6
alt1
–
send sync pattern
1 = AAh (Manchester/NRZ encoding) is sent as pad character.
0 = 00h (NRZI encoding) is sent as pad character.
Bit 5
FCS preset
0 = FCS is preset to all
‘
1
’
s (CRC V.41).
1 = FCS is preset to all
‘
0
’
s (CRC-16).
Bit 4
FCS mode
1 = Disables FCS generation and checking. The CD2481 treats the entire frame as
data.
0 = Normal FCS mode. The CD2481 generates and appends CRC on transmit and
validates CRC on receive using the CRC polynomial selected through the CRC Poly-
nomial Select register.
Bit 3
Idle mode
0 = idle in Flag mode
1 = idle in Mark mode
Bits 2:0
Character Count
–
specifies the number of synchronous characters sent.
COR3
–
Bisynchronous Mode
Bit 7
Send pad character
0 = CD2481 does not send any pad characters.
1 = CD2481 sends pad characters before sending SYN when coming out of the Mark
Idle mode.
Bit 6
S55 = Send pad pattern
0 = hex AA is sent as pad character.
1 = hex 55 is sent as pad character.
npad2
npad1
npad0
0
0
0
Reserved
0
0
1
1 pad character sent
0
1
0
2 pad characters sent
0
1
1
3 pad characters sent
1
0
0
4 pad characters sent
101
–
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
Sndpad
S55
FCSPre
FCS
Idle
DisCRC
npad1
npad0