STUCK-FAULT DIAGNOSIS METHOD FOR VARIABLE DELAY CONTROL CIRCUIT AND MEMORY CONTROLLER WITH VARIABLE DELAY CONTROL CIRCUIT

摘要

PROBLEM TO BE SOLVED: To make a diagnosis, in a shorter test time than before, as to presence or absence of a stuck fault which has occurred in a variable delay control circuit.SOLUTION: A stuck-fault diagnosis method for a variable delay control circuit comprises: switching the number of connections of a delay circuit which transfers data signals by plural switch circuits, depending on a control value received from plural control registers via plural control lines; calculating an exclusive logical OR of logical values appearing on two control lines of the plural control lines by each of plural exclusive OR circuits; retaining the logical values output from the exclusive OR circuits in plural diagnosis registers; setting the control registers to logical 0 in a variable delay control circuit which calculates a logical OR of the logical values output from the exclusive OR circuits, by an OR circuit; detecting a stuck fault of a logical 1 which has occurred in one of the control lines, based on the logical value output from the OR circuit; setting the control registers to logical 1; and detecting a stuck fault of a logical 0 which has occurred in one of the control lines, based on the logical value output from the OR circuit.SELECTED DRAWING: Figure 1