Coding system having data controlling mechanism activated when error is detected

A coding system includes a first coding part, a second coding part, a switch selecting one of the first and second coding parts, a multiplexer generating a multiplexed signal from a coded signal input via the switch, and a buffer memory temporarily storing the multiplexed signal. The coding system includes a controller which generates an invalidation signal, a reset signal and the select signal when the controller is notified of the occurrence of an error and which outputs the invalidation signal, the reset signal and the select signal to the multiplexer, the buffer memory and the switch. The select signal causes the switch to select the second coding part instead of the first coding part. The invalidation signal invalidates the coded signal supplied from the first coding part to the multiplexer before the coded signal from the second coding part is input to the multiplexer via the switch. The reset signal causes the multiplexed signal stored in the buffer memory to be erased.