Disc changing apparatus with error logging

Claim 1

An electronic system in which a microcomputer for system control is assembled, comprising: disc changing means for changing and transferring stacked discs from one of a stacked position or a playing position to other of said stacked position or said playing position, including a plurality of units each for performing a respective plurality of operations and each being controlled by said microcomputer; input means connected to said microcomputer for inputting a command to said microcomputer; memory means including non-volatile memory means in communication with said microcomputer such that when an error occurs in an operation of one of said plurality of units controlled by said microcomputer, error information identifying said operation in which said error occurred is written into said non-volatile memory means in response to a control signal from said microcomputer, wherein said non-volatile memory means has n memory addresses and said error information comprises a respective different error code for each of a plurality of possible operations, and error codes are sequentially written into said memory means at each occurrence of an error with memory addresses being sequentially incremented so that a latest n error codes are stored thereinto as history information; and output means for reading out said history information from said non-volatile memory means in response to a second control signal issued by said microcomputer, including error information at any arbitrary address designated by said microcomputer in response to a service command input through said input means, wherein said output means includes display means connected to said microcomputer for displaying said history information read out from said non-volatile memory means according to said second control signal from said microcomputer.