33.12.1 SMC_MODE.READ_MODE

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 MAIN_CLK cycles.

When the read operation is controlled by the NCS signal (SMC_MODE.READ_MODE = 0), the TDF field gives the number of MAIN_CLK 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 33-21. 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 33-22. TDF Period in NCS Controlled Read Operation (TDF = 3)