Apparatus and method to use a single reference component in a master-slave configuration for multiple circuit compensation

An apparatus, comprising:

• a single external impedance element having an impedance;
• a first plurality of impedance-generation devices coupled to the single external impedance element as a master circuit;
• a first control circuit coupled to the master circuit, the first control circuit capable to produce a reference impedance code corresponding to an impedance substantially matched to the impedance of the single external impedance element based on a number of activated devices in the first plurality of impedance-generation devices;
• a slave circuit coupled to the first control circuit to receive the reference impedance code from the first control circuit and having devices that are capable of activation based on the received reference impedance code;
• a second plurality of impedance-generation devices coupled to the slave 14 circuit;
• and
• a second control circuit coupled to the second plurality of impedance-generation devices, wherein at least one device of the second plurality of impedance-generation devices is responsive to the second control circuit to activate or deactivate based on a number of activated devices in the slave circuit to generate an impedance associated with a circuit attribute different from a circuit attribute associated with the first plurality of impedance-generation devices.

A system, comprising:

• a single external impedance element having an impedance and mounted on a motherboard;
• a master circuit on a chip and having impedance-generation devices that are capable of activation to provide an impedance that substantially matches the impedance of the external impedance element to compensate a circuit attribute, the master circuit being coupled to the single external impedance element by a pad or pin;
• a control circuit on the chip and coupled to the master circuit to generate a reference impedance code based on a number of activated devices in the master circuit;
• a slave circuit on the chip and coupled to the control circuit to receive a slave impedance code from the control circuit that is based on the reference impedance code and having devices that are capable of activation based on the received slave impedance code;
• and
• another plurality of impedance-generation devices on the chip and coupled to the slave circuit and capable of activation, based on a number of activated devices in the slave circuit, to provide another impedance to compensate a different circuit attribute.

A method, comprising:

• in a master circuit, activating at least one of a first plurality of impedance-generation devices associated to a first circuit attribute, until an impedance of the activated impedance-generation devices substantially matches an impedance of a single external impedance element;
• based on a number of activated devices in the first plurality of impedance-generation devices, generating a reference impedance code corresponding to the impedance of the activated impedance-generation devices;
• providing a slave impedance code that is based on the reference impedance code to a slave circuit;
• using the slave reference impedance code to activate at least one device in the slave circuit;
• and
• based on a number of activated devices in the slave circuit, activating at least one of a second plurality of impedance-generation devices to generate an impedance associated with a second circuit attribute different from the first circuit attribute associated with the first impedance-generation devices.

An article of manufacture, comprising:

• a machine-readable medium having instructions stored thereon to:
• for a master circuit, activate at least one of a first plurality of impedance-generation devices associated to a first circuit attribute, until an impedance of the activated impedance-generation devices substantially matches an impedance of a single external impedance element;
• based on a number of activated devices in the first plurality of impedance-generation devices, generate a reference impedance code corresponding to the impedance of the activated impedance-generation devices;
• provide a slave impedance code that is based on the reference impedance code to a slave circuit;
• use the slave reference impedance code to activate at least one device in the slave circuit;
• and
• based on a number of activated devices in the slave circuit, activate at least one of a second plurality of impedance-generation devices to generate an impedance associated with a second circuit attribute different from the first circuit attribute associated with the first impedance-generation devices.