
DS3181/DS3182/DS3183/DS3184
127
10.5.10 Framing Modes
The framing modes are selected independently of the line interface modes using the PORT.CR2.FM[5:0] control
bits. Different blocks are used in different framing modes. The bit error test (BERT) function can be enabled in any
mode. The LIU, JA and line encoder/decoder blocks are selected by the line mode (LM[2:0]) code.
The “- OHM” mode, also known as “externally defined frame mode”, is a mode that allow the use of the external
frame overhead bit mask pins TOHMIn, TOHMOn and ROHMIn. This mode allows external logic to select bit
locations where another level of framing can add overhead bits such as SONET/SDH overhead bits. Payload
loopback (PLB) is disabled in this mode. The “Clear-Channel—OHM Octet aligned” modes perform octet alignment
to the overhead mask for ATM and packets and the packets become octet stuffed instead of bit stuffed.
Table 10-32. Framing Mode Select Bits FM[5:0]
FM[5:0]
DESCRIPTION
LINE CODE
SYSTEM
FIGURE
0 00 000
DS3 C-bit
B3ZS/AMI/UNI
ATM/PKT
0 00 001
DS3 C-bit—OHM
UNI
ATM/PKT
0 00 010
DS3 C-bit Internal Fractional
B3ZS/AMI/UNI
ATM/PKT
0 00 011
DS3 C-bit External Fractional
B3ZS/AMI/UNI
ATM/PKT
0 00 100
DS3 C-bit PLCP
B3ZS/AMI/UNI
ATM
0 00 101
DS3 C-bit PLCP—OHM
UNI
ATM
0 00 110
DS3 C-bit Flexible Fractional
B3ZS/AMI/UNI
ATM/PKT
0 01 000
DS3 M23
B3ZS/AMI/UNI
ATM/PKT
0 01 001
DS3 M23—OHM
UNI
ATM/PKT
0 01 010
DS3 M23 Internal Fractional
B3ZS/AMI/UNI
ATM/PKT
0 01 011
DS3 M23 External Fractional
B3ZS/AMI/UNI
ATM/PKT
0 01 100
DS3 M23 PLCP
B3ZS/AMI/UNI
ATM
0 01 101
DS3 M23 PLCP—OHM
UNI
ATM
0 01 110
DS3 M23 Flexible Fractional
B3ZS/AMI/UNI
ATM/PKT
0 10 000
E3 G.751
HDB3/AMI/UNI
ATM/PKT
0 10 001
E3 G.751—OHM
UNI
ATM/PKT
0 10 010
E3 G.751 Internal Fractional
HDB3/AMI/UNI
ATM/PKT
0 10 011
E3 G.751 External Fractional
HDB3/AMI/UNI
ATM/PKT
0 10 100
E3 G.751 PLCP
HDB3/AMI/UNI
ATM
0 10 101
E3 G.751 PLCP—OHM
UNI
ATM
0 10 110
E3 G.751 Flexible Fractional
HDB3/AMI/UNI
ATM/PKT
0 11 000
E3 G.832
HDB3/AMI/UNI
ATM/PKT
0 11 001
E3 G.832—OHM
UNI
ATM/PKT
0 11 010
E3 G.832 Internal Fractional
HDB3/AMI/UNI
ATM/PKT
0 11 011
E3 G.832 External Fractional
HDB3/AMI/UNI
ATM/PKT
0 11 100
Reserved
0 11 101
Reserved
0 11 110
E3 G.832 Flexible Fractional
HDB3/AMI/UNI
ATM/PKT
1 00 0X0
DS3 Clear Channel
B3ZS/AMI/UNI
ATM/PKT
1 00 001
DS3 Clear-Channel—OHM
UNI
ATM/PKT
1 00 011
DS3 Clear-Channel—OHM Octet aligned
UNI
ATM/PKT
1 01 0X0
STS-1 Clear Channel
B3ZS/AMI/UNI
ATM/PKT
1 01 001
STS-1 Clear-Channel—OHM
UNI
ATM/PKT
1 01 011
STS-1 Clear-Channel—OHM Octet aligned
UNI
ATM/PKT
1 1X 0X0
E3 Clear Channel
HDB3/AMI/UNI
ATM/PKT
1 1X 001
E3 Clear-Channel—OHM
UNI
ATM/PKT
1 1X 011
E3 Clear-Channel—OHM Octet aligned
UNI
ATM/PKT