In general, the disclosure describes techniques for communication between at least one lead-borne device of an implantable lead and a medical device to which the lead is connected. The lead-borne device communicates with the medical device by modulating an impedance. The lead-borne device may communicate one or more bits of data to the medical device by selectively presenting either a first impedance or a second impedance to the medical device during one or more bit windows. The first and second impedance values may be respectively associated with first and second binary values, e.g., a high or one and low or zero.