WO2003101017A1 - Verfahren und schaltung zur taktumschaltung zwischen zwei bereitgestellten takten, insbesondere für peripherie-baugruppen von telekommunikationssystemen - Google Patents
Verfahren und schaltung zur taktumschaltung zwischen zwei bereitgestellten takten, insbesondere für peripherie-baugruppen von telekommunikationssystemen Download PDFInfo
- Publication number
- WO2003101017A1 WO2003101017A1 PCT/DE2002/001945 DE0201945W WO03101017A1 WO 2003101017 A1 WO2003101017 A1 WO 2003101017A1 DE 0201945 W DE0201945 W DE 0201945W WO 03101017 A1 WO03101017 A1 WO 03101017A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- clk
- clock
- output
- clock signals
- signal
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0685—Clock or time synchronisation in a node; Intranode synchronisation
- H04J3/0688—Change of the master or reference, e.g. take-over or failure of the master
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/0079—Receiver details
- H04L7/0083—Receiver details taking measures against momentary loss of synchronisation, e.g. inhibiting the synchronisation, using idle words or using redundant clocks
Definitions
- the invention relates to a method for switching between two clocks provided with the generic features of claim 1, 2 and 3 and circuits for performing such a method.
- the clock failure detection circuit is based on an external local clock oscillator.
- the local oscillator has, for example, a clock frequency of 25 MHz and is intended to recognize that the failure of clocks with a clock rate of, for example, 414 MHz It means that at least 17 consecutive clock pulses of the clock with 414 MHz must be missing before the clock failure can be recognized.
- the object of the invention is to improve a method or a circuit for switching the clock between two provided clocks, that is, from an active clock to a redundant clock.
- Clock selection signal is used primarily for routine checks of the clocks of the circuit.
- the switching process is carried out synchronized with a falling edge of the two clock signals to be subsequently output.
- An externally supplied signal can be used as the clock selection signal, but an internal signal can also be used if an external specification is undesirable or not necessary.
- the signal of the detector circuits is also to be regarded as an internal signal, on the basis of whose change the other clock is selected as the clock to be output.
- the fact that the switchover signal is synchronized with the respective reference clock and thereby also with the falling edge of this reference clock prevents the spikes caused by the hard switchover.
- the use of two flip-flops per switching direction of the signal used for clocking enables the avoidance of so-called metastability effects.
- the active clock can advantageously be switched off immediately with the synchronized clock selection signal, and the passive clock can be switched on after two separate clock periods. This leads to a very rapid switchover from the faulty or to the redundant clock when the selection button is not disturbed.
- the circuit or method preferably has an external oscillator which monitors both clocks. In this case, an error message is issued to a central instance, since the circuit will not work at all.
- a clocking known per se can be carried out particularly expediently, this being carried out both with the positive and with the negative clock edge of the redundant clock.
- the active clock can advantageously be doubled in terms of the clock duration by means of a divider device. At first glance, this leads to a delay in the detection of a clock failure that is delayed by half a clock period, but offers increased security due to a sufficient phase difference.
- Switching from one to the other clock cycle within two clock cycles after a change in the clock selection signal or after the detection of an error in the detector circuit enables a rapid switchover. This advantageously enables spikes to be prevented if there is at least one clock period between switching off the one clock signal and switching on the other clock signal.
- FIG. 1 shows a flowchart with a large number of different clocks or clock signals related to one another to illustrate the basic sequence of clock monitoring
- Fig. 3 shows such a diagram, in which the active clock for a comparison with the passive clock additionally divided by two, with a low failure
- Fig. 5 shows a circuit for performing a preferred method.
- two reference clocks Clk_l and Clk_2 are provided for a circuit arrangement.
- the first clock cycle Clk__l which is subsequently assumed to be the initially active clock cycle, a failure should occur after four and a half clock cycle periods shown so that it remains in the low state.
- the illustrated second clock cycle Clk_2, which is subsequently assumed to be the initially redundant or passive clock cycle, is to run continuously and, in the simplest case shown, is offset by 90 ° from the first active clock cycle Clk_l.
- the respective states of the first, active clock Clk_1 are clocked by clocking the first, active clock Clk_l with the second, redundant clock Clk_2 on the rising and falling edges of the redundant clock Clk_2.
- the clocking result when clocking with the positive or rising edges is shown as the third clock signal FF_P, the clocking with the negative or falling edges is shown as the fourth clock signal FF_N.
- the corresponding clock result or clock signal FF_N changes for the negative edge not, but remains constantly in a low state.
- the clock signal FF__P changes for clocking with the rising edge from the high to the low state.
- the EXOR output signal of the EXOR circuit is shown in the fifth line of the diagram.
- the lower half of the illustration in FIG. 1 shows the case in which the first, active clock Clk_l fails half a clock period earlier, that is to say remains in the high state.
- the failure during clocking with the negative edge is detected, which is determined by a corresponding switching of the clock signal FF_N for clocking with the negative edge three-quarter clock periods after the last switching process and is identified by a high state.
- the EXOR circuit recognizes this again when comparing the two clock signals FF_P and FF_N.
- An OR circuit which is arranged behind the EXOR circuits of the undelayed arrangement and the delayed arrangement, outputs the signal OR, which is used as a switchover signal.
- the corresponding detector circuit D1 is doubled, as can also be seen in FIG. 5, so that a second detector circuit D2 is available in parallel with the first detector circuit Dl.
- the inputs of the second detector circuit D2 are switched in reverse, so that the moment the first detector circuit D1 clocks the first clock Clk_l with the second clock Clk_2, the second detector circuit D2 clocks the second clock Clk_2 with the first clock Clk_l.
- one of the clock signals in FIG. 2 the active clock signal Clk_l, is first passed through a delay circuit and accordingly delayed by the amount DELAY. This can be carried out within each of the detector circuits, but can also be carried out if the detector circuit is doubled a common preliminary stage of these two detector circuits D1, D2.
- time diagrams are shown in the critical case in which the two reference clocks Clk_l and Clk_2 are in phase.
- the third line shows the clock signal Clk_l / 2 of an active clock Clk_l divided by two.
- a divider circuit which can be seen in Fig. 5, e.g. can be constructed by means of a flip-flop FF1.
- the clock signal Clk_l to be divided is applied to the clock input of the flip-flop FF1, while the output signal of the inverted output of this flip-flop FF1 is applied to the other input D.
- the reference clock Clk_2 and the divided clock signal Clk_l / 2 applied to two flip-flop circuits each consisting of two flip-flops FF2 and FF3 or FF4 and FF5.
- the reference clock Clk_2 is applied to the first clock input of both the first and the second flip-flops FF2 and FF3 or FF4 and FF5 of each flip-flop circuit
- the divided clock signal Clk_l / 2 to be clocked is applied to the respective second input.
- the output of the first flip-flop FF2 or FF3 leads to the input of the second flip-flop FF3 or FF5 of the corresponding flip-flop circuit.
- the flip-flops FF2 and FF3 of the first flip-flop circuit clock the divided clock Clk_l / 2 each on the rising edge of the second or reference clock Clk_2 and the flip-flops FF4 and FF5 of the second flip-flop circuit each clock at the falling edge of the reference clock Clk_2.
- the output signal FFP1 of the first flip-flop FF2 and the output signal FFP2 of the second flip-flop FF3 of the first flip-flop circuit which are shown as clock signals FF_P1, FF_P2 in the fourth and fifth lines in FIGS. 3 and 4 , are fed to the two inputs of an EXCLUSIVE-OR circuit, the output signal EXOR1 of which is shown as the sixth signal.
- the output signal FFN1 of the first flip-flop FF4 and the output signal FFN2 of the second flip-flop FF5 of the second flip-flop circuit which are shown as clock signals FF_N1, FF_N2 in the seventh and eighth lines in FIGS. 3 and 4 , are also fed to the two inputs of an EXCLUSIVE-OR circuit, the output signal EX0R2 of which is shown as the ninth signal.
- the two output signals EXOR1 and EX0R2 of the two EXCLUSIVE-OR circuits are supplied to an OR circuit, the output signal OR of which is shown in the tenth line.
- This output signal OR is ultimately applied to a flip-flop FF6, to the switching input of which the reference clock Clk_2 is applied and which samples with the falling edge.
- This final flip-flop FF6 is switched so that the switching process is synchronized with the falling edge of the second signal Clk_2 to be output after a disturbance of the first signal Clk_l.
- the circuit has a second, double detector D2, the structure of which is advantageously identical to the detector D1 described. At the second detector D2, however, the inputs are occupied in reverse to those of the first detector D1 in order to also enable the second clock Clk_2 to be monitored by clocking with the first clock Clk_l.
- the clock signals Clk_l and Clk_2 entering the overall arrangement are also applied to a further detector D3 with a local oscillator, which monitors whether both applied signals Clk_l and Clk_2 have failed.
- a corresponding error alarm is output for both clocks Clk_l and Clk_2 and is preferably fed to a central microprocessor ⁇ P for controlling the entire system.
- the microprocessor ⁇ P then at least switches this arrangement off.
- OR signals OR_N of the two detectors D1 and D2 are each fed to AND circuits, the second input of which is connected to a corresponding output
- Synchronization device SY is present, which is preferably controlled with the aid of a clock selection signal CLK_WAHL to determine a desired active clock.
- the outputs of the two AND circuits are in turn supplied to two further AND circuits, the second input of which is fed with the first clock signal Clk_l or Clk_2.
- the outputs of these two AND circuits are fed to an OR circuit whose The final output signal is the clock signal CLK_AUS, which is output from the overall circuit arrangement.
- the clock selection signal CLK_WAHL is present at the synchronization device SY to define one of the two active clock cycles Clk__l or Clk_2 desired as standard. This permanently has one of two states, e.g. high for the first clock signal Clk_l as the active clock and low for the second clock signal Clk_2 as the active clock.
- the clock selection signal CLK_WAHL is applied to two flip-flop circuits FF10 - FF13 or FF14 - FF17, at whose clock input the first or the second clock Clk_l, Clk_2 is applied.
- an inverter is advantageously interposed at the input of the clock selection signal CLK_WAHL.
- Each of the flip-flop circuits consists of four flip-flops FF10 - FF13 or FF14 - FF17, which are each connected in series, so that the output of a front flip-flop is present at the input of the subsequent flip-flop, that is for the first flip-flop circuit FF10 to FF11, FF11 to FF12, FF12 to FF13.
- the first clock Clk_1 is applied to the switching input in all flip-flops FF10-FF13 of the first flip-flop circuit
- the second clock Clk_2 is applied to all flip-flops FF14-FF17 in the second flip-flop circuit.
- the flip-flops FF10 - FF17 each switch on the falling edge.
- the output of the second flip-flop FF11 and the last flip-flop FF13 of the first flip-flop circuit are present at the two inputs of an AND circuit.
- a corresponding AND circuit is also provided for the second flip-flop circuit.
- the output of the first AND circuit is applied to an input of an OR circuit
- the output of the second of these AND Circuits is applied to an input of a second OR circuit.
- a signal is present at the two further inputs of these two OR circuits, which comes from an EXCLUSIVE OR circuit, at the inputs of which the two OR signals OR_N of the two detectors D1 and D2 are present.
- the outputs of the two OR circuits are fed to the AND circuits which are connected downstream of the two detectors D1 and D2.
- these last circuit elements correspond to a multiplexer MUX, which, on the basis of the signals input from the two detectors D1 and D2 and the two signals from the synchronization device SY, decide which clock pulse Clk_l or Clk_2 entered in the overall circuit arrangement at the output as an active clock pulse for further processing circuits is issued.
- MUX multiplexer
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Manipulation Of Pulses (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10297775T DE10297775D2 (de) | 2002-05-27 | 2002-05-27 | Verfahren und Schaltung zur Taktumschaltung zwischen zwei bereitgestellten Takten, insbesondere für Peripherie-Baugruppen von Telekommunikationssystemen |
AU2002317167A AU2002317167A1 (en) | 2002-05-27 | 2002-05-27 | Method and circuit for timed switching between two supplied clock pulses, particularly for peripheral components of telecommunication systems |
PCT/DE2002/001945 WO2003101017A1 (de) | 2002-05-27 | 2002-05-27 | Verfahren und schaltung zur taktumschaltung zwischen zwei bereitgestellten takten, insbesondere für peripherie-baugruppen von telekommunikationssystemen |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/DE2002/001945 WO2003101017A1 (de) | 2002-05-27 | 2002-05-27 | Verfahren und schaltung zur taktumschaltung zwischen zwei bereitgestellten takten, insbesondere für peripherie-baugruppen von telekommunikationssystemen |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003101017A1 true WO2003101017A1 (de) | 2003-12-04 |
Family
ID=29555571
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/DE2002/001945 WO2003101017A1 (de) | 2002-05-27 | 2002-05-27 | Verfahren und schaltung zur taktumschaltung zwischen zwei bereitgestellten takten, insbesondere für peripherie-baugruppen von telekommunikationssystemen |
Country Status (3)
Country | Link |
---|---|
AU (1) | AU2002317167A1 (de) |
DE (1) | DE10297775D2 (de) |
WO (1) | WO2003101017A1 (de) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0100076A2 (de) * | 1982-07-26 | 1984-02-08 | Siemens Aktiengesellschaft | Schaltungsanordnung zur Takterzeugung in Fernmeldeanlagen, insbesondere Zeitmultiplex-Digital-Vermittlungsanlagen |
US4598257A (en) * | 1983-05-31 | 1986-07-01 | Siemens Corporate Research & Support, Inc. | Clock pulse signal generator system |
US5748569A (en) * | 1996-12-19 | 1998-05-05 | Dsc Telecom L.P. | Apparatus and method for clock alignment and switching |
US5811995A (en) * | 1996-08-02 | 1998-09-22 | Advanced Micro Devices, Inc. | Circuit for switching between different frequency clock domains that are out of phase |
-
2002
- 2002-05-27 DE DE10297775T patent/DE10297775D2/de not_active Expired - Fee Related
- 2002-05-27 WO PCT/DE2002/001945 patent/WO2003101017A1/de not_active Application Discontinuation
- 2002-05-27 AU AU2002317167A patent/AU2002317167A1/en not_active Abandoned
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0100076A2 (de) * | 1982-07-26 | 1984-02-08 | Siemens Aktiengesellschaft | Schaltungsanordnung zur Takterzeugung in Fernmeldeanlagen, insbesondere Zeitmultiplex-Digital-Vermittlungsanlagen |
US4598257A (en) * | 1983-05-31 | 1986-07-01 | Siemens Corporate Research & Support, Inc. | Clock pulse signal generator system |
US5811995A (en) * | 1996-08-02 | 1998-09-22 | Advanced Micro Devices, Inc. | Circuit for switching between different frequency clock domains that are out of phase |
US5748569A (en) * | 1996-12-19 | 1998-05-05 | Dsc Telecom L.P. | Apparatus and method for clock alignment and switching |
Also Published As
Publication number | Publication date |
---|---|
AU2002317167A1 (en) | 2003-12-12 |
DE10297775D2 (de) | 2005-04-21 |
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