SYNCHRONIZATION CONTROL SYSTEM

• US 20140050232A1
• Filed: 10/18/2013
• Published: 02/20/2014
• Est. Priority Date: 04/19/2011
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Hirose, Akinori, Kawarada, Akira, Fukushima, Kazuto, Sugiura, Hideaki
• Granted Patent: US 9,209,919 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04J 3/0658 Clock or time synchronisation among packet nodes
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864

Abstract

According to an embodiment, the transmission processor of the master terminal includes a sending/receiving processor which sends a synchronization request demanding packet to a particular slave terminal and sends a synchronization reply packet when receiving a synchronization request packet from the slave terminal that has received the synchronization request demanding packet, and a synchronization controller which calculates a synchronization band from the time of the receipt of the data packet and from time information added to the received data packet to determine a synchronization state and which adjusts a correction amount in accordance with the synchronization state and sends an internal timing correction command to the timing generator.

Claims

1. A synchronization control system which respectively comprises transmission processors in a master terminal connected to a network and in a plurality of slave terminals and which synchronizes the slave terminals with the master terminal, wherein

the transmission processor of the master terminal comprises:

a transmission interface which holds a data packet to be sent or received and which acquires a receiving timing for synchronization control calculation when receiving a packet for synchronization control,

a timing generator which generates a constant internal timing,

a sending/receiving processor which sends a synchronization request demanding packet to a particular slave terminal and sends a synchronization reply packet when receiving a synchronization request packet from the slave terminal that has received the synchronization request demanding packet, and

a synchronization controller which calculates a synchronization band from the time of the receipt of the data packet and from time information added to the received data packet to determine a synchronization state and which adjusts a correction amount in accordance with the synchronization state and sends an internal timing correction command to the timing generator.

2. The synchronization control system according to claim 1, wherein the transmission processor of each of the slave terminals comprises a function of sending to the transmission processor of the master terminal in a long period an existence report packet to report that each of the slave terminals is connected to the network.

3. The synchronization control system according to claim 1, wherein the transmission processor comprises a terminal information manager which stores a table to manage information regarding each of the slave terminals and the state of synchronization control.

4. The synchronization control system according to claim 1, wherein the transmission interface comprises a register to acquire the receiving timing for synchronization control calculation, an address of the register is common to the slave terminals, and a single data packet receiving timing circuit is used.

5. The synchronization control system according to claim 1, wherein when the number of the slave terminals connected to the network is more than a given threshold, the sending/receiving processor adds, to the synchronization request demanding packet as information, the number of a slave terminal from which to demand a synchronization request, and multicast-sends the synchronization request demanding packet.

6. The synchronization control system according to claim 5, wherein the sending/receiving processor multicast-sends a demand cancel command packet for the slave terminal to send a synchronization request packet without waiting for a synchronization request demanding packet to be received from the master terminal when the number of the slave terminals connected to the network is less than the given threshold, and the sending/receiving processor sends a demand start command packet for the slave terminal to send a synchronization request packet after waiting for a synchronization request demanding packet to be received from the master terminal when the number of the slave terminals connected to the network has reached the given threshold.

7. The synchronization control system according to claim 2, wherein the transmission processor of each of the slave terminals comprises a terminal information manager which stores a table to manage information regarding each of the slave terminals and the state of synchronization control, and

the transmission processor of the master terminal multicast-sends an existence report packet in the same way as the transmission processor of each of the slave terminals, and when no existence report packet is received from the transmission processor of the master terminal for a given period of time, the slave terminal having the lowest terminal number serves as a proxy master, and the proxy master sends synchronization request demanding packets to the other slave terminals and uses the terminal information manager to manage the information regarding each of the slave terminals and the state of synchronization control.

8. A master terminal which is applied to a synchronization control system, the synchronization control system respectively comprising transmission processors in the master terminal connected to a network and in a plurality of slave terminals and synchronizing the slave terminals with the master terminal, wherein

the transmission processor of the master terminal comprises:

a transmission interface which holds a data packet to be sent or received and which acquires a receiving timing for synchronization control calculation when receiving a packet for synchronization control,

a timing generator which generates a constant internal timing,

a sending/receiving processor which sends a synchronization request demanding packet to a particular slave terminal and sends a synchronization reply packet when receiving a synchronization request packet from the slave terminal that has received the synchronization request demanding packet, and

a synchronization controller which calculates a synchronization band from the time of the receipt of the data packet and from time information added to the received data packet to determine a synchronization state and which adjusts a correction amount in accordance with the synchronization state and sends an internal timing correction command to the timing generator.

9. The master terminal according to claim 8, wherein the transmission processor comprises a terminal information manager which stores a table to manage information regarding each of the slave terminals and the state of synchronization control.

10. The master terminal according to claim 8, wherein the transmission interface comprises a register to acquire the receiving timing for synchronization control calculation, an address of the register is common to the slave terminals, and a single data packet receiving timing circuit is used.

11. The master terminal according to claim 8, wherein when the number of the slave terminals connected to the network is more than a given threshold, the sending/receiving processor adds, to the synchronization request demanding packet as information, the number of a slave terminal from which to demand a synchronization request, and multicast-sends the synchronization request demanding packet.

12. The master terminal according to claim 11, wherein the sending/receiving processor multicast-sends a demand cancel command packet for the slave terminal to send a synchronization request packet without waiting for a synchronization request demanding packet to be received from the master terminal when the number of the slave terminals connected to the network is less than the given threshold, and the sending/receiving processor sends a demand start command packet for the slave terminal to send a synchronization request packet after waiting for a synchronization request demanding packet to be received from the master terminal when the number of the slave terminals connected to the network has reached the given threshold.