Fault detection system for a telephone exchange

• US 3,908,099 A
• Filed: 09/27/1974
• Issued: 09/23/1975
• Est. Priority Date: 09/27/1974
• Status: Expired due to Term

• Current Assignee: Microtel Limited-Microtel Limitee
• Original Assignee: John R. Dufton, Robert A. Borbas
• Inventors: Borbas, Robert A., Dufton, John R.
• Primary Examiner(s): Claff, Kathleen H.
• Assistant Examiner(s): Olms, Douglas W.
• Application Number:
  US05/510,093
• Time in Patent Office: 361 Days
• Field of Search: 179/175.2R,175.2C,18AG 340/172.5
• US Class Current: 379/9
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs
• CPC Class Codes: G06F 11/0763 by bit configuration check, e.g. of formats or tags
• CPC Class Codes: G06F 11/20 using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
• CPC Class Codes: G06F 11/2733 Test interface between tester and unit under test
• CPC Class Codes: H04Q 3/54591 Supervision, e.g. fault localisation, traffic measurements, avoiding errors, failure recovery, monitoring, statistical analysis

Abstract

A fault detection system transfers the control of the telephone exchange from the presently on line common data bus and its associated dedicated subsystems over to an off line common data bus and its associated dedicated subsystems. The fault detection system comprises a monitoring means for monitoring the operation of the on line common data bus and its associated dedicated subsystems for providing a first multiple bit status word indicative of the operative conditions of the on line common data bus and its associated dedicated subsystems, means coupled to the monitoring means for storing the first multiple bit status word, status word updating means coupled to the monitoring means and the storing means for updating the first status word to indicate the current operative status of the on line common data bus and associated dedicated subsystems and for setting a bit within the first status word indicating a request for a first test routine, and means for transmitting the first status word to the on line central processor for causing it to obtain a first test instruction from its program memory and for acting thereupon. The fault detection system additionally comprises clock means coupled to the monitoring means for setting a predetermined time period and for providing a control signal when the on line common bus and its associated dedicated subsystems fail to complete the first test instruction routine within the predetermined time and transfer means coupled to the clock means and to the dedicated subsystems for transferring the control of the telephone exchange from the on line common data bus and its associated dedicated subsystems over to the off line common data bus and its associated dedicated subsystems in response to the control signal.

Claims

1. In a telephone exchange of the type which includes a first common data bus, a second common data bus, a first plurality of subsystems dedicated only to said first common data bus, a second plurality of subsystems dedicated only to said second common data bus and a third plurality of subsystems common to both of the first and second common data buses, wherein only one common data bus and its associated dedicated subsystems are operatively on line with the third plurality of subsystems at any instant in time for providing requested telephone subscriber service, and whrein each of the first and second dedicated subsystems includes a program memory for storing a plurality of operational codes including a plurality of test instructions, and a central processor for controlling the operation of its associated dedicated subsystems and the third plurality of subsystems in response to its program memory operational codes, a fault detection system for transferring the control of the telephone exchange from the presently on line common data bus and its associated dedicated subsystems over the off line common data bus and its associated dediCated subsystems, said fault detection system comprising:

monitoring means for monitoring the operation of the on line common data bus and its associated dedicated subsystems for providing a first multiple bit status word indicative of the operative conditions of the on line common data bus and its associated dedicated subsystems;

means coupled to said monitoring means for storing said first multiple bit status word;

status word updating means coupled to said monitoring means and said storing means for updating said first status word to indicate the current operative status of the on line common data bus and associated dedicated subsystems and for setting a bit within said first status word indicating a request for a first test routine;

means for transmitting said first status word to the on line central processor for causing it to obtain a first test instruction from its program memory and for acting thereupon;

clock means coupled to said monitoring means for setting a predetermined time period and for providing a control signal when the on line common bus and its associated dedicated subsystems fail to complete the first test instruction routine within said predetermined time; and

transfer means coupled to said clock means and to said dedicated subsystems for transferring the control of the telephone exchange from the on line common data bus and its associated dedicated subsystems over to the off line common data bus and its associated dedicated subsystems in response to said control signal.

2. A fault detection system in accordance with claim 1 wherein said monitoring means also provides the off line common data bus and its associated dedicated subsystems with a second multiple bit status word, wherein one of the bits of the second multiple bit status word indicates its off line status and wherein said updating means also sets a bit in said second multiple bit status word to cause the off line central processor to initiate a second test routine, said second test routine including fewer instructions than said first test routine.

3. A fault detection system in accordance with claim 1 wherein said first common data bus and said second common data bus each comprises a plurality of lines and wherein said monitoring means includes means for detecting inoperative lines of said on line common data bus and for setting a bit in said first status word indicating the presence of an inoperative on line common data bus line.

4. A fault detection system in accordance with claim 1 wherein each central processor includes a bit time counter comprising a shift register for providing a shifting bit to initiate each operational code instruction and wherein said monitoring means includes a time base fault detector coupled to said bit time counter for detecting the absence of said shifting bit and for setting a bit in said first status word responsive to said detection.

5. A fault detection system in accordance with claim 2 further comprising interlocking means coupled to said first and second common data buses for precluding the off line data bus from transmitting data to the third plurality of subsystems.

6. A fault detection system in accordance with claim 5 further comprising write enable control means and printing means, said write enable control means being coupled to said monitoring means for setting a write bit in said second system status word and to said interlocking means for enabling said off line common bus and its associated dedicated subsystems to transmit to said printing means.

7. A fault detection system in accordance with claim 1 wherein each subsystem is assigned a discrete unique address and wherein said fault detection system additionally comprises an address selecting means, a comparator means, and a printing means, said address selecting means for selecting one of said discrete unique addresses, said comparator means being coupled to said address selecting means and to said on line common bus for comparing said selected Address with the address of the subsystem transmitting data onto the on line bus, and coupled to said monitoring means for setting a print status bit in said first system status word when said selected address matches the address of the subsystem transmitting data onto the on line bus, and said printing means being responsive to said print status bit for printing the data received from the subsystem having said selected address.

8. A fault detection system in accordance with claim 1 additionally comprising an executive cycle timer and wherein the performance of a predetermined number operational codes by each central processor is an executive cycle, said executive cycle timer being coupled to said monitoring means and reset by the on line central processor at the beginning of each central processor executive cycle and adapted to establish a predetermined time interval to set an interrupt bit in said first status word for resetting the central processor when an on line central processor executive cycle exceeds said predetermined time interval.

9. A central processor in accordance with claim 8 further comprising an interrupt status means coupled to said executive cycle timer for enabling said interrupt bit to reset the on line central processor.

10. A fault detection system in accordance with claim 1 further comprising means for periodically initiating a test call for service to be processed by the on line common bus and its associated dedicated subsystems in conjunction with said third plurality of subsystems and said monitoring means including test call timing means for establishing a minimum test call execution time and providing a test call fail signal when the time required by said on line common bus and its associated dedicated subsystems in conjunction with said third plurality of subsystems to process said test call exceeds said minimum test call execution time, counting means coupled to said monitoring means for counting the test call fail signals and for setting a test call fail bit in said first system status word when a predetermined number of consecutive test call fail signals have been counted, said transfer means being responsive to said test call fail bit set for transferring control of the telephone exchange to the off line common bus and its associated dedicated subsystems.

11. A fault detection system in accordance with claim 10 wherein said predetermined number is two.

12. A fault detection system in accordance with claim 1 wherein each subsystem is assigned a discrete unique address and wherein said fault detection system includes address selecting means for selecting one of said unique discrete addresses, comparator means coupled to the on line data bus and to said address selecting means for comparing the address of the subsystem on the on line data bus to said selected address and control terminating means coupled to said comparator for terminating control of the telephone exchange by the on line bus and its associated subsystems when the address of the subsystem on the on line data bus matches said selected unique discrete address.

13. A fault detection system in accordance with claim 12 wherein said transfer means is responsive to said control terminating means for transferring control of the telephone exchange to the off line bus and its associated dedicated subsystems after the control by said on line bus and its associated dedicated subsystems has been terminated.

14. A fault detection system in accordance with claim 1 further comprising multiple transfer detecting means coupled to said transfer means for precluding further transfers after a predetermined number of transfers have occurred within a preset time period.

15. A fault detection system in accordance with claim 1 wherein each subsystem is assigned a unique discrete address and wherein the on line central processor transmits the address of each subsystem it controls over its associated data bus and wherein said fault detection system further comprises address storing meanS for storing the address of each subsystem controlled by the on line central processor.

16. A fault detection system in accordance with claim 1 wherein each central processor has access to said storing means and wherein one central processor addresses said storing means with a direct address and the other central processor addresses said storing means with a complement address.

17. A fault detection system in accordance with claim 1 wherein said storing means is a 20 bit store and wherein said storing means is coupled to the central processor over first, second and third lines,

18. A fault detection system in accordance with claim 17 wherein said first, second and third lines are 8 bit lines and wherein said third line utilizes only its first four bits.