Pattern memory circuit for integrated circuit testing apparatus

A pattern memory circuit for an integrated circuit testing apparatus, which comprises:

• a pattern memory having an address input, a data input, a read/write input, and a data output;
• a CPU in which a sequence program for diagnosis of the pattern memory is written, the CPU for generating a start signal, an allocation mode signal representing an allocation mode, a self-check signal representing a self-check mode, and a read enable signal;
• an address generating circuit having an address input from the CPU and an address output, and adapted to generate addresses of the pattern memory;
• an address/data generating circuit having an address/data input from the CPU and an address/data output, adapted to generate addresses of the pattern memory different from the addresses generated by the address generating circuit during the allocation mode, and adapted to generate data during the self-check mode;
• an end detection circuit having an end address input from the CPU and an end detect output, and adapted to detect completion of the operation of the address generating circuit to notify the CPU of the completion;
• a control circuit receiving the start signal from the CPU and the end detect signal from the end detection circuit, the control circuit being actuated by the start signal to generate a control signal for allowing operation of the address generating circuit, the address/data generating circuit, and the end detecting circuit, and to generate read and write cycle signals representing alternating read and write cycles;
• a first selector for selecting the address/data output of the address/data generating circuit during a write cycles during the allocation mode, and for otherwise selecting the address output of the address generating circuit, the selection being output as a signal to the address input of the pattern memory;
• a second selector for selecting the address/data output from the address/data generating circuit during the self-check mode, and for otherwise selecting the data output from the pattern memory, the selection being output as a signal to the data input of the pattern memory;
• and
• a comparator receiving signals from the data output and the data input of the pattern memory as inputs, the comparator adapted to compare data read from the pattern memory and data forwarded from the second selector during the self-check mode to determine coincidence therebetween, the comparator outputting a fault signal when coincidence is not determined;
• whereby, during a first allocation mode, data stored in the pattern memory is transferred from first addresses to second addresses within the pattern memory;
• whereby, after the first allocation mode and during the self-check mode, data from the address/data generating circuit is written into the first addresses during absence of a read enable signal from the CPU, and the data in the pattern memory is read out during presence of a read enable signal from the CPU and compared in the comparator with the data from the address/data generating circuit previously written in;
• and
• whereby, after the self-check mode and during a second allocation mode, the data in the second addresses is transferred back to the first addresses.