SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE

摘要

In the upgrading of the ECU, an ECU 1 to be a master notifies other ECUs 1a and 1b of change of an ACK slot length. The ECUs 1a and 1b change the ACK slot length into an ACK slot length received from the ECU 1. At this time, the changed ACK slot length is stored in each register 5a provided in the ECUs 1a and 1b. Subsequently, the master ECU 1 transmits an upgrade data to each of the ECUs 1a and 1b at a communication speed corresponding to the changed ACK slot length. After completion of the upgrade, the ECU 1 notifies of change of the ACK slot length into the original ACK slot length. After receiving this, the ECUs 1a and 1b reset the ACK slot length to the notified original ACK slot length.