Nortel DMS-100 Series Maintenance Manual page 39

The DDL message bits and field names
DDL bits
Bits 15 through 17
Bits 18 and 19
Bits 20 through 23
Bit 24
Note: If the M-, A-, or S-fields do not change between messages, the 8085
microprocessor sends the previous field patterns. The RCS, at the other
end, also sends the same patterns. The 8085 microprocessor sends
information to the UP when a DDL field changes. The RCS does not
transmit idle patterns.
When RCS shelf groups AB and CD operate in Mode II, these shelf groups
use the C-field. This field carries information for shelves A, B, C, and D.
This information includes control of assignment and deassignment of
subscribers to DS-1 channels, hook changes, and activation of the PCM
looping test.
Speech/signaling between the SMS and the RCS
The SMS and RCS use A- and B-bit messaging to exchange speech and
signal information. The A- and B-bits are 1 or 0. To construct messages,
the system assembles the SMS and RCS bits in the following patterns:
steady state 0
steady state 1
modulated 0
modulated 1
These patterns indicate different signaling states. The SMS sends the
following signaling information to the RCS for each channel:
—end—
DMS-100 Family SMS Maintenance Manual XPM10 and up
Maintenance overview 1-23
(continued)
Field name
Maintenance field (M-field). The
M-field on the A-link carries
information for all shelves. This
M–field controls card and customer
loop testing.
Alarm data link field (A-field). The
A-field on the A-link carries alarm
and system control information for
all shelves.
Protection line switch field (S-field).
The S-field on the A-link controls the
switching of the DS-1 protection
link.
Spoiler bit field (fixed pattern of 1)