39.7.12.1 SMC M0DE.READ M0DE

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.

The following figure 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 39-19. TDF Period in NRD Controlled Read Access (TDF = 2)

The following figure shows the read operation when controlled by NCS (SMC MODE.READ MODE = 0) and SMC MODE.TDF CYCLES = 3.

Figure 39-20. TDF, (i.e. Data Float Time), Period in NCS Controlled Read 0peration (TDF = 3)