The H.110 Bus & Clock Modes
• 6-4 •
The H.110 Basic Rate ISDN Board
5 - a local network (TE port) with auto-fallback to CT_NETREF_2
For submode 1 and 2, argument bb will select the frequency of the
CT_NETREF signal. The choice is:
00 - 8 kHz. (frame rate)
Note that on this board other CT_NETREF rates are not supported.
For submodes 3-5, argument bb will select one of the Basic Rate ISDN
interfaces. This interface must be operating as a TE (terminal equipment).
For submodes 4 and 5, the optional argument c will specify the frequency
of the selected CT_NETREF source.
For all modes, argument a should be set to 0. On H.100 boards, this
argument is used to select the legacy bus compatible clocks that the board
will supply. As the H.110 bus is not compatible with the SC or MVIP bus,
the only valid option is 0, no compatibility clocks provided.
6.2.3 Secondary Master Modes
When a board is operating as a secondary master, it uses the other clock
signal as a source, i.e. if a board is the secondary master for CT clock B,
it uses CT clock A as a source and provides CT clock B. If the primary
clock fails, the secondary master then becomes the clock master.
Typically, one board will be set as the master for clock A and another
board as the secondary master for clock B, or vice versa. If the clock
source specified by the submode is either of the CT_NETREF signals or
a local network, the board will automatically fall-back on that source if the
primary clock should fail. If set to free-run, it will fall back to a PLL that
was locked to the primary master clock.
In all secondary master modes, if the primary master fails, the board will
automatically become the new primary master. If the original primary
master is restored, the clock mode for the original secondary master must
be reset.