Can the nIRQ interrupt output pin on an EZRadioPRO device be shared with other devices?
Or to ask the question another way, is the nIRQ output pin on EZRadio/EZRadioPRO (Si4455 and Si446x devices) an open-drain pin that may be direct-tied in parallel with nIRQ pin(s) of other chips or devices?
No. The nIRQ output pin on Si4455 and Si446x chips is a driven pin (i.e., a push-pull output architecture) whenever the chip is in an active state. The only state in which the nIRQ pin is not driven to a logic level is when the chip is in SHUTDOWN mode (SDN pin = HIGH). In this state, the nIRQ output pin is not directly driven to a logic level, but is internally pulled HIGH by a weak pull-up resistor. Thus if the system application is designed such that the nIRQ pins of multiple devices are directly tied together in parallel, the system must ensure that the EZRadioPRO chip is in SDN mode when the other device(s) are functional, and vice versa.