Digital spread spectrum circuitry

A method for spreading the electromagnetic emissions of a generated clock signal that is created in response to a reference clock signal, the method comprising the steps of:

• providing a delay line in the path of the reference clock signal;
• providing an offset in the reference clock signal;
• and
• adjusting trim units in the delay line in a pre-determined pattern during consecutive clock cycles,
• wherein the step of providing an offset comprises providing a trim unit adjustment of +2 prior to starting the pre-determined pattern and wherein the pre-determined pattern comprises providing trim unit adjustments of +1, +2, 0, +2, −1, +2, −2, +2 and +2 during nine consecutive clock cycles.

A method for spreading the electromagnetic emissions of a generated clock signal that is created in response to a reference clock signal, the method comprising the steps of:

• providing a delay line in the path of the reference clock signal;
• and
• adjusting trim units in the delay line in a pre-determined pattern during consecutive clock cycles,
• wherein the pre-determined pattern comprises providing trim unit adjustments according to a pattern selected from the following group of patterns:
• −1, 0, −2, 0, −3, 0, −4, 0 and 0 during nine consecutive clock cycles;
• −1, 0 and 0 during three consecutive clock cycles;
• −1, 0, −2, 0 and 0 during five consecutive clock cycles;
• −1, 0, −2, 0, −3, 0 and 0 during seven consecutive clock cycles.

A method for spreading the electromagnetic emissions of a generated clock signal that is created in response to a reference clock signal, the method comprising the steps of:

• providing a delay line in the path of the reference clock signal;
• providing an offset in the reference clock signal;
• and
• adjusting trim units in the delay line in a pre-determined pattern during consecutive clock cycles,
• wherein the step of providing an offset comprises providing a trim unit adjustment of +1 prior to starting the pre-determined pattern, and wherein the pre-determined pattern comprises providing trim unit adjustments of 0, +1, −1, +1 and +1 during five consecutive clock cycles.

A method for spreading the electromagnetic emissions of a generated clock signal that is created in response to a reference clock signal, the method comprising the steps of:

• providing a delay line in the path of the reference clock signal;
• providing an offset in the reference clock signal;
• and
• adjusting trim units in the delay line in a pre-determined pattern during consecutive clock cycles,
• wherein the step of providing an offset comprises providing a trim unit adjustment of +1 prior to starting the pre-determined pattern, wherein the pre-determined pattern comprises providing trim unit adjustments of 0, +1, −1, +1, −2, +1 and +1 during seven consecutive clock cycles.