Any access can be extended by an external device using the NWAIT input signal of the SMC. The SMC_MODE.EXNW_MODE field on the corresponding chip select must be set either to “10” (Frozen mode) or “11” (Ready mode). When SMC_MODE.EXNW_MODE is set to “00” (disabled), the NWAIT signal is simply ignored on the corresponding chip select. The NWAIT signal delays the read or write operation in regards to the read or write controlling signal, depending on the Read and Write modes of the corresponding chip select.