A memory system includes a memory controller coupled to at least one memory device via high-speed data and request links. The timing and voltage margins of the links are periodically calibrated to reduce bit error. The high-speed request links complicate calibration because commands issued over the uncalibrated request links can be erroneously interpreted by the memory device. Misinterpreted commands can disrupt the calibration procedure (e.g., a write command might be misinterpreted as a power-down command). The memory controller addresses this problem using a separate, low-speed control interface to issue a filter command that instructs the memory device to decline potentially disruptive requests when in a calibration mode.
