A co-worker was recently tasked with providing cross training for a product which I do not have much experience with on the topic of T1 troubleshooting and alarm clearing. After getting this class, I decided it would be fun to put together something similar (in blog format) for CS1000 T1 alarm clearing.
Receiving an alarm
There are a variety of PRI alarms, but we’ll take one of them as an example:
Interpreting the alarm
Some systems have part of the alarm lookup database on-system which can be accessed via the Overlay Loader (OVL000 and a > prompt) using the ERR command
If the alarm library is loaded with that alarm, then you’ll get the help text. If not, you’ll get an error:
OVL441 Help text not found for error code: [code]
All alarms in the documentation are in 4 digit length after the 3 letter alarm group code. DTA are digital trunking alarm. 021 is the specific alarm. Finding it in the documentation can be done by searching for DTA0021. From the documentation we get the alarm text:
Frame alignment alarm persisted for 3 seconds
Responding to the alarm
Let’s talk briefly about some of the different tools available for troubleshooting:
- LD 60 / Digital Trunk Interface and Primary Rate Interface Diagnostics
- LD 96 / D-channel Diagnostics
- LD 20 / Print Routine 1 – Use to identify a trunk’s association with a Route Datablock (RDB).
- LD 21 / Print Routine 2 – Used to list trunk members to determine trunk group associations between PRIs/DTIs.
- LD 22 / Print Routine 3 – Used to print common equipment (CEQU) and D-channel configuration (ADAN DCH)
- LD 73 / Digital Trunk Interface – Used to check clocking (DDB)
Digital Trunk Interface and Primary Rate Interface Diagnostics
DTI and PRI diagnostics (LD 60) cover a variety of tasks, you can: enable/disable loops, clocking, individual bearer channels (B-channels or BCH) and print/clear counters. For a full list of commands, see the Software Input/Output Reference – Maintenance (NN43001-711).
STAT [loop channel]
|Show status of all loops or loop specified. Loop status include loop state and BCH state.
SSCK [loop shelf]
|Show system clock. Includes which circuit is being used for primary clocking and clock state.
||Swap clock from current active to current standby
||Set clock controller tracking to PCK/Primary Clock, SCK/Secondary Clock, FRUN/Free run-no clock.
|ENCH [loop channel]
||Disable loop when idle. Disables any IDLE channel then waits till other channels are disabled. Loops until all B-channels are disabled then disables loop.
|DSCH [loop channel]
DCH Diagnostics covers: enable/disable d-channels, d-channel monitors, and work with MSDL or TMDI cards. On larger legacy 1000M systems, the Multipurpose Serial Data Link (MSDL) card is used to provide D-channel functionality. On smaller 1000M systems and newer 1000E systems, the D-channel functionality is built into the TMDI (T1 Multipurpose Digital Interface) card. In this article, we will not be discussing troubleshooting D-channel diagnostics for MSDL cards on larger 1000M systems.
STAT DCH [dch]
|Show status of all/specific DCH.
|ENL DCH [dch]
|DIS DCH [dch]
|STAT TMDI [card]
||Show status of TMDI. (CS1000M small system)
|STAT TMDI [loop shelf card]
||Show status of TMDI. (CS1000E)
|DIS TMDI [card]
||Disable TMDI. (CS1000M small system)
|DIS TMDI [loop shelf card]
||Disable TMDI. (CS1000E)
|SLFT TMDI [card]
||Selftest TMDI. (CS1000M small system) Performs multiple hardware tests to verify TMDI is functional.
|SLFT TMDI [loop shelf card]
||Selftest TMDI. (CS1000E) Performs multiple hardware tests to verify TMDI is functional.
|ENL TMDI [card [fdl]]
||Enable TMDI. (CS1000M small system) Optional FDL/Full Download of TMDI EPROM.
|ENL TMDI [loop shelf card [fdl]]
||Enable TMDI. (CS1000E) Optional FDL/Full Download of TMDI EPROM.
|PLOG DCH [dch]
Print Routine 1
The command architecture for the CS1000 is built on the older Meridian-1 systems, which in turn is built upon the even older SL-1 systems. When the SL-1 hardware architecture was replaced or improved, Nortel introduced new commands or Overlays as needed, all while keeping the essential command structure introduced with the first SL-1 system in the mid-1970s.
Print Routine 1 covers peripheral programming, including the bearer channel (BCH) configuration for a T1. From the Terminal Number configuration of a BCH, it is possible to identify the route membership for a particular channel, and by extension the T1. (While it is technically possible to configure different channels within a T1 to belong to multiple routes, I’ve never seen this and excepting MUXed circuits I am not aware of any reason why it might be done.)
Print Routine 2
Print Routine 2 covers customer datablock configurations, including route datablock (RDB) settings. By using the List Trunk Members command, it is possible to identify all of the BCH (and by extension all the T1s) that belong to a particular route (i.e., trunk group).
Print Routine 3
Print Routine 3 covers hardware and system configuration data, such as the Common Equipment (CEQU) datablock and Action Device and Number (ADAN) datablock, the latter of which is used to store information about D-channel configuration.
Digital Trunk Interface
When building a PRI/DTI in a CS1000 system for the first time, the Clock Controller and Alarm Threshold values must be set. For systems in the USA, the DDB (digital data block) configuration record contains the relevant configuration settings.
Diagnostics vs Print Routines & configuration
LD 60 and 96 are used primarily for diagnostics. Overlays 20-22 and 73 would be used to configuration review to assist with diagnostics. For the purposes of this article, we will assume that a configuration issue is not at fault. Perhaps in some future article I might cover PRI configuration in more detail.
NN43001-611 Software Input/Output Reference – Administration
NN43001-711 Software Input/Output Reference – Maintenance
NN43001-712 Software Input/Output Reference – System Messages
NN43001-301 ISDN Primary Rate Interface Installation and Commissioning