A logic circuitry package for association with a replaceable print apparatus component comprises: logic and a serial data bus interface, wherein the serial data bus interface is to interface with a serial data bus of a print apparatus, and, wherein the logic is, in response to a first command sent to the logic circuitry package via the serial data bus connected to the serial data bus interface, the first command including a time period, to generate a low voltage condition on the serial data bus for a duration based on the time period, and, after the duration, return to a default voltage condition on the serial data bus.