Abstract: An arrangement and method for switching a single destination data channel to a different destination without losing any data messages. Such a switch is required, for example, when a switch is made to a standby control unit and the messages originally destined for the original active control unit must be sent to the standby. Received messages are drained from the source prior to making the switch. Appropriate data is copied from the active unit to the standby so that the standby unit is in a state to start accepting newly queued messages from the source.

Abstract: In order to provide reliable backup memory for the operational memory (RAM) of a control unit, two segments of a memory with write protect facility are used. Only one of these segments contains the backup memory at any one time, but the other segment may be updated with a new release. Write protect is removed from one of these segments only when an update is taking place. The software for controlling initialization of the operational memory from the backup memory is stored in the backup memory. Extensive checks are performed before accepting an update of the backup memory or an initialization of the operational memory.

Abstract: An Electrically Erasable Programmable Read Only Memory (EEPROM) provides backup and initialization data for random access memory (RAM) in a control unit. In order to update the EEPROM with new releases of a program and data, the EEPROM is divided into two segments, each with a separately controllable write enable voltage. Advantageously, this allows a new release to be written into one segment of a single EEPROM without erasing the other segment until the newly written segment has been verified.

Abstract: An Electrically Erasable Programmable Read Only Memory (EEPROM) provides backup and initialization data for random access memory (RAM) in a control unit. In order to update the EEPROM with new releases of a program and data, the EEPROM is divided into two segments, each with a separately controllable write enable voltage. Advantageously, this allows a new release to be written into one segment of a single EEPROM without erasing the other segment until the newly written segment has been verified. The software for controlling an update of the EEPROM is stored in RAM and the software for controlling an initialization of the RAM from the EEPROM is stored in the EEPROM. Extensive checks are performed before accepting an update of the EEPROM or an initialization of the RAM.