CIRCUIT DELAY MONITORING APPARATUS AND METHOD

摘要

A circuit delay monitoring apparatus has a ring oscillator with a plurality of delay elements, a signal transition being propagated through the delay elements of the ring oscillator, and a plurality N of sampling points being distributed around the ring oscillator. Selection circuitry selects, in dependence on the indication of the current location of the signal transition generated by the fine sampling circuitry, one of the M transition counter circuits whose associated location is greater than said predetermined amount from the current location of the signal transition. Output generation circuitry then generates a count indication for a reference time period dependent on a sampled count value of the transition counter circuit selected by the selection circuitry, the indication of the current location of the signal transition within the ring oscillator, and reference count data relating to the start of the reference time period.

主权项

1. A circuit delay monitoring apparatus comprising:
a ring oscillator comprising a plurality of delay elements, a signal transition being propagated through the delay elements of the ring oscillator; a plurality N of sampling points distributed around the ring oscillator; fine sampling circuitry configured to sample signal values at each of the plurality of sampling points under control of a reference clock signal, in order to generate an indication of a current location of the signal transition within the ring oscillator; coarse sampling circuitry comprising M transition counter circuits, where M is at least 2 and less than N, each transition counter circuit being connected to an associated location within the ring oscillator and configured to increment a count value each time the signal transition passes the associated location, the coarse sampling circuitry being configured to sample the count value under control of the reference clock signal, the M transition counter circuits being connected to the ring oscillator so that, at any point in time, the separation between the current location of the signal transition and the associated location of at least one of said M transition counter circuits will be greater than a predetermined amount; selection circuitry configured to select, in dependence on the indication of the current location of the signal transition generated by the fine sampling circuitry, one of said M transition counter circuits whose associated location is greater than said predetermined amount from the current location of the signal transition; and output generation circuitry configured to generate a count indication for a reference time period dependent on a sampled count value of the transition counter circuit selected by the selection circuitry, the indication of the current location of the signal transition within the ring oscillator, and reference count data relating to the start of the reference time period.