16.13.1 READ_MODE

Setting 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 TDF_CYCLES MCK cycles.

When the read operation is controlled by the NCS signal (READ_MODE = 0), the TDF_CYCLES field in HSMC_MODEx gives the number of MCK cycles during which the data bus remains busy after the rising edge of NCS.

The figure TDF Period in NRD Controlled Read Access (TDF = 2) illustrates the Data Float Period in NRD-controlled mode (READ_MODE = 1), assuming a data float period of two cycles (TDF_CYCLES = 2). The figure TDF Period in NCS Controlled Read Operation (TDF = 3) shows the read operation when controlled by NCS (READ_MODE = 0) and the TDF_CYCLES parameter equals 3.

Figure 16-18. TDF Period in NRD Controlled Read Access (TDF = 2)
Figure 16-19. TDF Period in NCS Controlled Read Operation (TDF = 3)