A semiconductor integrated circuit having a test circuit for collecting test data at any time based on interaction with an external source is provided. A communication circuit receives a data frame that is transferred to a data buffer. Data portions are transferred to a test unit of a test circuit. A counter starts a count operation based on a system clock when count information is transferred. If one of the data portions indicates the transferred data is test data, and another portion indicates a data collection specification command, the test unit outputs decoded address data to interact with a circuit-under-test when the counter completes the count operation based on another portion of the frame. A data buffer is supplied with the address data to facilitate storage of the data transferred from the circuit-under-test.