Clockmaster Limitation with SC bus and DM3 Trunk
Symptom:
It is impossible to change the primary clockmaster in the DCM to NETREF1, or FrontEnd1. As a result, frame slippage and failed faxes may occur under high density when the only other option (Internal Oscillator) is used as the primary clockmaster.
Reason for the problem:
When a system's board configuration is such that there is a card which must use the SC bus instead of H.100, and the only T1/E1 frontend card in the system is of DM3 architecture, it is a known permanent restriction that the primary clockmaster must be set to Internal Oscillator. An example would be a system containing these boards:
DM/IP481
MSI PCI Global
DISI 32
The MSI PCI Global card forces the bus to be set to SC. Although there is a T1 frontend on the DMIP board, this board is a DM3 architecture, so attempts to clock off the frontend of this board will fail. Attempting to clock off NETREF1 will fail as well, since this option requires the system to use the CT bus, and the MSI card prevents that.
Workaround:
The only option is to add or change some of the boards in the system so that either:
1.) All boards in the system use the CT bus
or
2.) There is a card of Springware architecture in the system which has a T1/E1 frontend.
In above example, option 1 could be achieved by replacing the MSI card with another DISI card. Option 2 could be achieved simply by adding a D/240JCT to the system.
Product List
DMV/JCT and MSI cards
Glossary of Acronyms / Terms
SC bus = 4MHz bus type that older Dialogic cards use
CT/H.100 bus = 8MHz bus type used by newer Dialogic cards
Frontend1 = A setting in DCM which tells the system to clock off of the T1 or E1 line coming into a digital board
NETREF1 = A setting in DCM which tells the system to clock off of the CT bus
Internal Oscillator = A setting in DCM which tells the system to clock off of an oscillator located on the specified board. Not recommended for production use.
First published: 06-Apr-2008
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