Setting SMC_MODE.READ_MODE to 1 indicates to the SMC that the NRD signal is responsible for turning off the tri-state buffers of the external memory device. The Data Float Period then begins after the rising edge of the NRD signal and lasts SMC_MODE.TDF_CYCLES MCK cycles.
When the read operation is controlled by the NCS signal (SMC_MODE.READ_MODE = 0), the TDF field gives the number of MCK cycles during which the data bus remains busy after the rising edge of NCS.
Figure 1 illustrates the Data Float Period in NRD-controlled mode (SMC_MODE.READ_MODE =1), assuming a data float period of 2 cycles (SMC_MODE.TDF_CYCLES = 2). Figure 2 shows the read operation when controlled by NCS (SMC_MODE.READ_MODE = 0) and SMC_MODE.TDF_CYCLES = 3.
