There are a few embedded FRC commands. The user can implement a custom FRC command too. See User FRC Codes intervals for allowed custom FRC command values and FrcValue event.
All embedded FRC commands prepare returned FRC values within the shortest predefined FRC response time of 40 ms (corresponds to _FRC_RESPONSE_TIME_40_MS constant). Only in the case of Memory read and Memory read plus 1 command the FRC response time depends on the DPA Request that is specified by the user and executed before the FRC value is returned. Event FrcResponseTime is not implemented for embedded FRC commands, therefore, FRC response time returns 0xFF for them.