Amtelco infinity series - Clock Modes

The H.110 Bus & Clock Modes• 6-2 •
The H.110 Basic Rate ISDN Board
6.2 Clock Modes
The H.110 bus specification defines a variety of clock signals. Two clock
signals CT bus A and CT bus B are provided for redundancy. In addition,
two signals called CT_NETREF_1 and CT_NETREF_2 are defined which
may be referenced to an external clock source such as a T1 or E1 span.
These signals exists to aid in recovery if the primary clock source should
fail.
The clock mode must be set before any connections can be made with
other boards. The clock mode is set using the Set Clock command
“SCmsabbc”, where m is the clock mode, s is the sub-mode, and a, bb, and
c are additional arguments used to select clock sources and specify
compatibility modes. This command takes the same form on all Infinity
Series H.100 boards. Because of this, some of the possible options are not
relevant to the H.110 boards, but the format is retained to make it easier to
create applications that are portable between the two bus structures.
The default clock mode on a power up is to provide a local clock, but to
neither source clock signals to the bus or derive the clock from the bus.
The possible clock modes are:
0 no clocks to or from the bus
1 clocks slaved to the CT bus
2 the board is clock master CT bus clock A
3 the board is clock master CT bus clock B
4 the board is secondary master for CT bus clock A
5 the board is secondary master for CT bus clock B
Connections are possible only when all boards within a system are
synchronized to the same clock. Only one board in a system can provide
the H.110 bus clock. The other boards in the system must slave their
internal clocks to the master. If the H.110 Basic Rate ISDN Board is to
use the H.110 bus clock, this clock must be provided by another board
before switching can be accomplished.