# US 2014/0191813 A1 · Test Solution for a Random Number Generator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0191813 A1 - Document ID: US20140191813A1 - Status: Published application - Kind: A1 - Application number: 14/193,932 - Filed: 2014-02-28 - Published: 2014-07-10 - Earliest claimed: 2012-09-06 - Assignees: Silicon Image, Inc. - Applicants: Silicon Image, Inc. - Inventors: Chinsong Sul; Hyukyong Kwon; Andy Ng - Web page: https://patentgrep.com/patent/US20140191813A1 ## CPC - H03K 3/0315: {Ring oscillators} - G06F 7/58: Random or pseudo-random number generators - G06F 7/588: {Random number generators, i.e. based on natural stochastic processes} - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A random number generator and method for testing the same are described. In one embodiment, the random number generator comprises one or more ring oscillator structures, each of the one or more ring oscillator structures having a ring oscillator for use in generating random numbers and having a test structure to reconfigure the ring oscillator into a testable structure. ## Claims ### Claim 1 A random number generator comprising: one or more ring oscillator structures, each of the ring oscillator structure having an output connected through a network of logic gates and storage cells for random number generation, each of the ring oscillator structures comprising: a ring oscillator configured to generate random numbers, and a test structure to reconfigure a ring oscillator structure into a testable structure for testing the ring oscillator structure and the network of logic gates and storage cells, ### Claim 2 (depends on 1) The random number generator of claim 1, wherein the testable structure comprises a test access port. ### Claim 3 (depends on 2) The random number generator of claim 2, wherein the test access port provides access for performing structural and functional tests and identifying a fault location in the random number generator. ### Claim 4 (depends on 2) The random number generator of claim 2, further comprising a multiplexer to selectively enable a functional feedback path from an output of an inverter chain of a ring oscillator structure to an input of the inverter chain based on a signal. ### Claim 5 (depends on 4) The random number generator of claim 4, wherein the signal is an output of a first gate responding to first and second inputs, the first input being the output of an XNOR gate that applies XNOR logic to a test input and an output of the multiplexer and the second input being based on or more or more test mode signals. ### Claim 6 (depends on 1) The random number generator of claim 1, wherein each of the one or more ring oscillator structures has a test interface for performing test functions, the test interface having a multiplexer to provide, based on a select input, either a test input or a value based on a feedback of a test output, the select input based on one or more test mode signals. ### Claim 7 (depends on 1) The random number generator of claim 1, further comprising: an XOR network having a plurality of inputs coupled to outputs of the one or more ring oscillator structures and having an output to provide a test response; a plurality of registers, each register providing a test input to the XOR network and to receive an output of one of the one or more ring oscillator structures; and a plurality of multiplexers having a pair of inputs and an output, the output of each multiplexer in the plurality of multiplexers coupled to an input of a ring oscillator of a distinct one of the one or more ring oscillator structures, the inputs being coupled to a test input and an output of one of the plurality of registers. ### Claim 8 (depends on 7) The random number generator of claim 7, wherein the plurality of registers configured to capture test results and indicate faulty ring oscillator structures. ### Claim 9 (depends on 7) The random number generator of claim 7, wherein the plurality of multiplexers are controlled by a test mode signal, and wherein a change in the test mode signal causes a dynamic reconfiguration of an output test path associated with the ring oscillator structures without reprogramming of the plurality of registers. ### Claim 10 (depends on 1) The random number generator of claim 1, wherein the ring oscillator comprises an odd number of inverters connected back-to-back and configured to produce an oscillatory output. ### Claim 11 (depends on 1) The random number generator of claim 1, wherein the test structure is coupled to provide either an observability chain input or a test input to the ring oscillator structure and to receive the oscillatory output as a feedback from the ring oscillator. ### Claim 12 (depends on 1) The random number generator of claim 1, wherein the ring oscillator, after reconfiguration by the test structure, allows one or more of a structural stuck-at test and a functional test of the ring oscillator. ### Claim 13 (depends on 1) The random number generator of claim 1 wherein the ring oscillator structures comprise a group of ring oscillator structures connected in a serial chain, wherein a test output of a last of the ring oscillator test structures in the serial chain is fed back for use with the test input to a first ring oscillator structure in the chain. ### Claim 14 (depends on 1) The random number generator of claim 1, further comprising a transition counter configured to measure transitions of a ring oscillator structure at a ring oscillator output until a test mode is changed. ### Claim 15 (depends on 14) The random number generator of claim 14, wherein the test structure starts a functional test in response to a change of test mode from an external input controlled test mode. ### Claim 16 (depends on 1) The random number generator of claim 1, wherein the test structure outputs in steady-state to allow at least one of the ring oscillator structures to appear as an inverter without asynchronous feedback. ### Claim 17 (depends on 1) The random number generator of claim 1, wherein the one or more ring oscillator structures using the test structures collectively identify an odd number of path struck-at faults based on complimentary polarity in bypass and functional paths of the one or more ring oscillator structures. ### Claim 18 A random number generator comprising: one or more ring oscillator structures, each of the one or more ring oscillator structure having an output connected through a network of logic gates and storage cells for random number generation, each of the one or more ring oscillator structures comprising: a ring oscillator for generating random numbers, and a test structure to reconfigure a ring oscillator structure into a testable structure for testing the ring oscillator structure and the network of logic gates and storage cells an XOR network having a plurality of inputs coupled to outputs of the one or more ring oscillator structures and having an output to provide a test response; a plurality of registers, each of the registers coupled to provide a test input to the XOR network and to receive an output of one of the one or more ring oscillator structures; and a plurality of multiplexers having a pair of inputs and an output, the output of each of the multiplexers coupled to an input of a ring oscillator structure, the inputs coupled to a test input and an output of one of the plurality of registers. ### Claim 19 (depends on 18) The random number generator of claim 18, wherein the test structure comprises a test access port. ### Claim 20 (depends on 19) The random number generator of claim 19, wherein the test access port provides access for structural and functional tests and identifying of a fault location in the random number generator.