Implementation example with STR711F

AN2394

10/13

To avoid this and decrease the CPU load, a solution based on the capability to read the

whole SPI Flash memory with a single read data instruction is implemented:

–

the first time a data byte is needed, a call to Start_Read_Sequence function is

made. This initiates a read data byte sequence from the SPI Flash. This is done by

driving the S line low to select the device, then the read data instruction is

transmitted followed by 24-bit address. This function exits and keeps the S line

low, with the SPI Flash still being selected.

The next routine which needs to read a byte from the SPI Flash has only to generate a

dummy byte on the Serial Data Input line of the SPI Flash and get the data on the Serial

Data Output line. So only step 4 is performed each time a data is read from the SPI Flash

which significantly reduces the CPU overhead.

When the playback is finished, the read data byte sequence is terminated by driving Chip

Select high.