System and method for establishing consistent memory contents in redundant systems

A copying device of a redundant system, comprising:

• a first device to read data from a memory of a control device;
• a second device to write the data to the memory of the control device;
• a third device to receive address information about memory areas to which a write access has been performed;
• a fourth device to synchronize the address information with a marking memory having memory areas storing information to which a write access has been performed, by sending data from the memory areas of the memory which are entered in the marking memory and the address information of the data to a first copying device;
• a fifth device to receive the data and the address information of the data from a second copying device;
• and
• a sixth device to enter the data in the memory of the control device in accordance with the address information received.

A method for establishing consistent memory contents in a redundant system, having an active control unit and an inactive control unit, each having a processing unit with an interface unit and a memory, comprising:

• monitoring the memory of the active control unit by a memory monitoring module of the active control unit, the memory having address information relating to memory areas to which a write access has been performed and which is forwarded by the memory monitoring module of the active control unit to a copying device of the active control unit;
• synchronizing the address information supplied by the memory monitoring module of the active control unit by the copying device of the active control unit with a marking memory of the active control unit, in which the memory areas to which a write access has been performed are entered;
• sending data from the memory areas entered in the marking memory of the active control unit by the copying device of the active control unit by a link to the copying device of the inactive control unit, whereby corresponding bits are reset in the marking memory of the active control unit;
• storing the data received by the copying device of the inactive control device by the link at the address in the memory of the inactive control device at the same address stored in the memory of the active control device;
• entering a number of remaining memory areas of the memory of the active control device which have been modified by a write access;
• and
• defining a limit value for the number such that when the number fails to reach the value, additional write accesses to the memory of the active control device are prevented until the remaining memory areas of the memory of the active control device which have been modified by the write access have been transferred to the memory of the inactive control device,
• wherein the method is executed until the memory areas of the memory of the active control device which have been modified by a write access have been transferred to the memory of the inactive control device.

A system for establishing consistent memory contents in a redundant system, comprising:

• an active control unit and an inactive control unit, each having a processing unit with an interface unit and a memory, wherein
• the memory of the active control unit is monitored by a memory monitoring module of the active control unit, the memory having address information relating to memory areas to which a write access has been performed and which is forwarded by the memory monitoring module of the active control unit to a copying device of the active control unit,
• the address information supplied by the memory monitoring module of the active control unit is synchronized by the copying device of the active control unit with a marking memory of the active control unit, in which the memory areas to which a write access has been performed are entered,
• data from the memory areas entered in the marking memory of the active control unit is sent by the copying device of the active control unit by a link to the copying device of the inactive control unit, whereby corresponding bits are reset in the marking memory of the active control unit, and
• the data received by the copying device of the inactive control device by the link is stored at the address in the memory of the inactive control device at the same address stored in the memory of the active control device.

A system in a redundant system, comprising:

• a first device to read data from a memory of a control device;
• a second device to write the data to the memory of the control device;
• a third device to receive address information about memory areas to which a write access has been performed;
• a fourth device to synchronize the address information with a marking memory having memory areas storing information to which a write access has been performed, by sending data from the memory areas of the memory which are entered in the marking memory and the address information of the data to a first copying device;
• a fifth device to receive the data and the address information of the data from a second copying device;
• and
• a sixth device to enter the data in the memory of the control device in accordance with the address information received.