Data receiver circuitry in the device is provided with one or more error signal output leads. An error signal on such a lead includes an error indication as soon as possible after the associated low level circuitry detects a data error. The timing of such an error indication is compared to the timing of noise from various possible noise sources in the device. The noise source that produced significant noise closest in time prior to the error indication is identified as the noise source responsible for the data error that caused the error indication.