JPS62112433A - Clock distribution equipment - Google Patents

Abstract

PURPOSE:To allow all cases to receive a clock signal of the same phase by detecting a reciprocating time of a high frequency pulse train reciprocated between a clock distributor and each case via a transmission delay measuring line and sending a clock signal having a delay say automatically based on the reciprocating time. CONSTITUTION:When a pulse train reciprocated through a transmission delay measuring line 12a is a returned pulse train (b), the pulse number counted by a pulse count circuit 6a is 6-pulse (c). Suppose that the delay amount of the clock signal at the reception end of the cases 9a, 9b is set as 200ns, a further delay of 140ns=200ns-120ns/2 is to be given. According to the result of discrimination, the pulse count circuit 6a controls a selector 8a selecting the tap of a delay line 7 to send a clock signal having a delay of 140ns from the selector 8a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a clock distribution device constituting a digital communication device.

[Conventional technology]

Conventionally, in this type of large-scale digital communication equipment that spans multiple chassis, the method of sending clock signals with the same phase to each chassis is to make all supply cables the same length regardless of the distance between the chassis. was there.

[Problem that the invention seeks to solve]

In the conventional clock signal transmission method described above, the length of all supply cables is fixed, so the maximum length, including equipment expansion, may be several tens of meters or even more than 100 meters. Laying such a long cable is a waste of equipment and is also undesirable from an aesthetic point of view.

[Means for solving problems]

In order to solve these problems, the present invention provides a high-frequency pulse generation circuit that is connected to a transmission delay measurement line and generates a high-frequency pulse train, a pulse counting circuit that counts pulses to detect the delay amount of a clock signal, and A clock distribution device is provided with a transmission delay amount measuring section having a transmission delay amount measuring section, and a clock signal sending section having a delay line provided with a tap and a selector for selecting the tap.

[Effect]

In the present invention, the round-trip time of the high-frequency pulse train that went back and forth between the clock distribution device and each housing via the transmission delay measurement line is detected1, and the delay is automatically set based on this round-trip time. Sends out a clock signal having a certain amount.

〔Example〕

FIG. 1 shows a digital communication device to which an embodiment of the clock distribution device according to the present invention is applied. In FIG. 1, 1 is a clock distribution device according to this embodiment, 2 is a clock generator, and 3 is a clock signal supply cable 10a, R.
Transmission delay measurement unit 4 is for measuring the cable delay, which is the delay of the clock signal in ob, in all cases 9
This is a clock signal sending section that sends out a clock signal with a delay amount set according to the cable delay in order to receive clock signals of the same phase at the terminals a and 9b.

The transmission delay measurement section 3 is connected to a clock signal supply cable 10.
a, a clock signal line 11a in 10b;

A transmission delay amount measurement line 12a is provided alongside 11b.

12b and generates a high-frequency pulse train, and clock supply cables 10a and 10
The pulse counting circuit 6a and 6b are provided for counting pulses in order to detect the delay amount of the clock signal. The clock signal sending unit 4 has a delay line 7 provided with several types of taps for generating a delay amount according to the cable delay, and a delay line 7 that is installed to correspond to the clock supply cables 10a and 10b and has a delay amount according to the cable delay. Selector 8 for selecting a tap to output a clock signal
It is composed of a and 8b. Each housing 9a, 9b receiving the clock signal is connected to the clock supply cable lOa.
, 10b.

The high-frequency pulse generation circuit 5 generates the transmission pulse train shown in FIG.
and is supplied to pulse counting circuits 6a and 6b.

If the pulse train that has traveled back and forth on the transmission delay measurement line 12a and returned is like the return pulse train shown in FIG. 2 (bl), the number of pulses counted in the pulse counting circuit 6a is as shown in As shown, there are 6 pulses.

The frequency of the sending pulse train shown in Figure 2+a) is 50MHz
In this case, the number of counted pulses is 6, which means 6X2
A delay of 0ns=120ns is the transmission delay measurement line 12a.
This indicates that this occurred in If each housing 9a,
If the delay amount of the clock signal at the receiving end of 9b was set to 200ns, then the delay amount would be 140ns = 200ns.
It is sufficient to provide a delay of ns - 120ns/2.

According to this determination result, the pulse counting circuit 6a controls the delay line 7.
The selector 8a selects a tap, and the selector 8a sends out a clock signal with a delay of 140 ns.

[Effects of the Invention] As explained above, the present invention provides for transmitting a high-frequency pulse train that is intermittently sent back and forth between a clock distribution device and each housing that receives a clock signal via a transmission delay measuring line of a lamp. A pulse counting circuit detects the round trip time of the high frequency pulse train within the clock signal supply cable, and the round trip time of the transmission delay measurement line is detected so that a predetermined delay amount is obtained at the clock receiving end of each housing. By automatically selecting the taps of the delay line based on the time, it is possible to select the delay amount of the clock signal to be sent, so there is no need to use long cables of the same length, and there is no need to be conscious of the cable length. This has the effect of making it possible to receive clock signals of the same phase in all cases.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a digital communication device to which an embodiment of the clock distribution device according to the present invention is applied, and FIG. 2 is a time chart for explaining this embodiment. DESCRIPTION OF SYMBOLS 1... Clock distribution device, 2... Clock generation section, 3... Transmission delay amount measuring section, 4... Clock signal sending section, 5... High frequency pulse generation circuit, 6a ,
6b...Pulse counting circuit, 7...Delay line, 8
a, 8b...Selector, 9a, 9b...Housing,
10a, 10b...Clock supply cable, lla
, 11b...clock signal line, 12a, 12b...
...Transmission delay amount measurement line.

Claims (1)

[Claims] In a clock distribution device that supplies clock signals via a clock signal supply cable to multiple cases constituting large-scale digital communication equipment, transmission for measuring cable delay, which is the delay of the clock signal in the clock signal supply cable. a delay amount measuring section; and a clock signal sending section that sends out a clock signal with a delay amount set according to the cable delay in order to receive clock signals of the same phase in all the cases, The measuring section includes a high-frequency pulse generation circuit that is connected to a transmission delay amount measurement line that is installed alongside the clock signal line in the clock signal supply cable and generates a high-frequency pulse train, and a high-frequency pulse generation circuit that is connected to the transmission delay amount measurement line and that generates a transmission delay amount measurement line that is connected to the transmission delay amount measurement line that is connected to the clock signal line in the clock signal supply cable. and a pulse counting circuit that counts pulses in order to detect the amount of delay, and the clock signal sending section includes a delay line provided with a tap for generating a delay amount corresponding to the cable delay, and a pulse counting circuit that counts pulses to detect the amount of delay. and a selector for selecting the tap in order to output a delay amount according to the clock distribution device and a clock signal supplied through the pair of transmission delay measurement lines for reciprocating the high-frequency pulse train that is sent out intermittently. The pulse counting circuit detects the reciprocating time of the high-frequency pulse train within the clock signal supply cable, and a predetermined amount of delay is detected at the clock receiving end of each of the housings. automatically select the delay line taps based on the round trip time as obtained;
A clock distribution device characterized by being able to receive clock signals of the same phase in all cases.