TMXF28155 Supermapper
155/51 Mbits/s SONET/SDH x28/x21 DS1/E1
Data Sheet
June 2002
474
Agere Systems Inc.
20 M13/M23 MUX/DeMUX Block Functional Description
(continued)
FCS Generation.
Once the last buffer byte is transmitted, the HDLC controller either transmits a closing flag byte
(when M13_TDL_FCS = 0 (
Table 291 on page 225
)), or it first appends the 2-byte ITU-T FCS with the necessary
zero stuffing before sending the closing flag (when M13_TDL_FCS = 1). In either case, the HDLC controller sets
M13_TDL_DONE (
Table 229 on page 204
) to 1 after the transmission of the frame is complete. For testing pur-
poses, the user can send corrupted FCS bytes by clearing M13_TDL_FCS to 0 and filling the last 2 bytes in the
buffer with an incorrect CRC value.
LAPD Example.
T1.107 defines three standard LAPD messages that may be transmitted on the path maintenance
data link. After the opening flag, each of these messages contains 79 bytes of address, control, and information.
These are followed by the 2-byte FCS and the closing flag.
To transmit one of these messages using the internal HDLC transmitter, the microprocessor should first set
M13_TDL_ACT (
Table 291
) to 1, M13_TDL_NTRNL (
Table 291
) to 1, and M13_TDL_NTRNL_ACT (
Table 291
) to
0. This causes the continuous generation of flag bytes.
The microprocessor may then fill buffer 0 with the first 64 bytes of the message and fill bytes 0 through 14 of buffer
1 with the last 15 bytes prior to the FCS of the message. By setting M13_TDL_BUF0_END (
Table 291
) to 0,
M13_TDL_BUF1_END (
Table 291
) to 1, and M13_TDL_BYTE_END[5:0] (
Table 292 on page 225
) to 001110, the
microprocessor can indicate that 79 buffer bytes are to be transmitted.
The microprocessor can then set M13_TDL_FCS to 1 and M13_TDL_NTRNL_ACT to 1. This will cause the inter-
nal HDLC transmitter to send the 79 buffer bytes, append the FCS and closing flag, set M13_TDL_DONE to 1, and
resume continuous flag transmission.
If the same LAPD message is to be transmitted later without first having transmitted a different message, the
microprocessor only needs to toggle M13_TDL_NTRNL_ACT to 0 and back to 1, since the values of the other con-
trol parameters and the buffer bytes are not modified by the internal HDLC transmitter.
20.8 AIS/Idle Insertion
The AIS/idle insertion block can be provisioned to operate in the normal mode (M13_DS3_FORCE_AIS = 0
(
Table 288 on page 223
) and M13_DS3_FORCE_IDLE = 0 (
Table 288
)), generate DS3 AIS
(M13_DS3_FORCE_AIS = 1), or generate DS3 idle (M13_DS3_FORCE_AIS = 0 and M13_DS3_FORCE_IDLE =
1).
In the normal mode, data from the M23 multiplexer is passed unchanged to the B3ZS encoder block.
During AIS insertion (M13_DS3_FORCE_AIS = 1), the generated DS3 frame is altered by overwriting the informa-
tion bits with an alternating 1010 . . . pattern, starting with a 1 after each overhead bit. In addition, the X bits are
overwritten with ones, and the C bits are overwritten with all zeros (T1.107 and T1.404).
During idle signal generation (M13_DS3_FORCE_AIS = 0 and M13_DS3_FORCE_IDLE = 1), the information bits
are overwritten with 11001100 . . ., starting with 11 after each overhead bit. The X bits are overwritten with ones. In
the M23 mode (M13_M23_CBP = 1 (
Table 272 on page 219
)), the C bits are overwritten with all zeros. In the C-bit
parity mode, the C bits are passed unchanged (T1.107 and T1.404).
20.9 B3ZS Encoder (GR-499)
The transmit DS3 device output can either be in the form of unipolar data (M13_DS3POS_DATA when
M13_BIPOLAR = 0 (
Table 272 on page 219
)) or positive data and negative data (M13_DS3POS_DATA, and
M13_DS3NEG when M13_BIPOLAR = 1). If M13_BIPOLAR = 1, the DS3 data is B3ZS encoded with
M13_DS3POS_DATA = 1 indicating a positive pulse and M13_DS3NEG = 1 indicating a negative pulse.