Cost effective semiconductor devices and semiconductor systems with reduced test time

Abstract

A semiconductor system may include a first semiconductor device and a second semiconductor device. The first semiconductor device may output a clock signal, a test mode signal and command address signals. The second semiconductor device may repeatedly write and read out data into and from a plurality of memory cells sequentially selected by addresses that are sequentially counted or may repeatedly write and read out the data into and from specific memory cells selected by a specific address among the addresses, according to the clock signal and the command address signals in response to the test mode signal.