| 摘要 |
PURPOSE:To easily test the memory contents of a ROM and also to prevent the outsiders from decoding the program of a ROM by comparing a cyclic code signal which is received from a cyclic code check circuit with another cyclic code signal obtained from a normal ROM in order to test the contents of the ROM data. CONSTITUTION:An address switch means 2 switches the address to a ROM 1. A data conversion means 3 converts the parallel data 104 read out of the ROM 1 for each address with an access to the means 2 into the serial data 105. A cyclic code check circuit 4 converts the serial data obtained via the means 3 into a cyclic code and outputs it to the outside. Then the cyclic code signal received from the circuit 4 is compared with another cyclic code signal obtained from another normal ROM 1. Thus the contents of the ROM can be tested. Thus it is possible to easily test the contents of the ROM and also to prevent the outsiders from decoding the program of the ROM. |
