CD2481
—
Programmable Four-Channel Communications Controller
114
Datasheet
9.2.2
Channel Option Register 1 (COR1)
COR1
–
HDLC Mode (Not used in PPP mode)
If any options specified in this register are changed, an initialize command must be given to
CD2481 through the Channel Command register.
Bit 7
Address field length option
0 = Address field is 1 octet in length
1 = Address field is 2 octets in length
Bit 6
Clear detect for X.21 data transfer phase
0 = Clear detect disabled
1 = Clear detect enabled
A clear is defined as two consecutive all zero receive characters with the CTS* pin
high.
Bits 5:4
Addressing modes
00 = no address recognition
01 = 4 * 1 byte
10 = 2 * 2 byte
If this bit is set, RFAR1, RFAR2, RFAR3, and RFAR4 should contain the address
to be matched. If AFLO is set to
‘
1
’
, an address match is made against the RFAR1
and RFAR2 pair or the RFAR3 and RFAR4 pair.
Bits 3:0
Inter-frame flag option
Defines the minimum number of flags transmitted before a frame is started.
0
1
1
0
MNP4/ARAP
0
1
1
1
Reserved
1
0
0
0
Programmable Sync
chmd3
chmd2
chmd1
chmd0
Protocol
Register Name: COR1
Register Description: Channel Option Register 1
Default Value: x
’
00
Access: Byte Read/Write
Intel Hex Address: x
’
13
Motorola Hex Address: x
’
10
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
AFLO
ClrDet
AdMd1
AdMd0
Flag3
Flag2
Flag1
Flag0
Flag 3
Flag 2
Flag 1
Flag 0
0
0
0
0
minimum of 1 opening flag, with
shared closing/opening flags
permitted
0
0
0
1
through
minimum number of opening flags
sent
1
1
1
1