Transmit driver impedance calibration techniques for bidirectional serializer/deserializer

A calibration system comprising:

• a first serializer/deserializer (SerDes) comprising a first transmit driver;
• a second SerDes comprising a second transmit driver and connected to the first SerDes via a data transmission line;
• wherein the first SerDes further comprises circuitry for controlling an impedance of the first transmit driver in accordance with an impedance code received form the second SerDes;
• and
• wherein the second SerDes further comprises:
• circuitry for, for each of a plurality of impedance code values:
• transmitting the impedance code value to the first SerDes, the first SerDes for using the impedance code value for controlling the impedance of the first transmit driver;
• measuring an eye height of an eye of a predetermined data sequence transmitted by the second SerDes;
• circuitry for determining which one of the measured eye heights comprises a maximum eye height for the first transmit driver;
• and
• circuitry for communicating to the first SerDes the impedance code value associated with the one of the eye heights comprising the maximum eye height for the first TX driver.

A calibration system comprising:

• a first serializer/deserializer (SerDes) comprising a first transmit driver, wherein an impedance of the first transmit driver is controlled by an impedance code;
• a second SerDes comprising a second transmit driver and connected to the first SerDes via a data transmission line, the second SerDes further comprising circuitry for measuring an eye of the second transmit driver, the circuitry comprising:
• a sampler for sampling data at an output of the second transmit driver;
• an error counter for comparing data output from the sampler with local data and outputting an error signal indicative of whether the data output from the sampler is the identical to the local data;
• a delay tuning block for tuning a delay clock of the sampler.