Standard SPI mode is selected when the Mode option in the Vivado IDE is set to Standard. The relevant parameters in this mode are:
•Enable STARTUPEn Primitive
Note: The STARTUPE2 primitive is applicable for 7 series devices. The STARTUPE3 primitive is applicable for Ultrascale™ devices.
•No. of Slaves
The properties of the core in standard SPI mode, including or excluding a FIFO, are described as:
•The choice of inclusion of FIFO is based on the Enable FIFO parameter. FIFO Depth parameter is linked to Enable FIFO parameter. FIFO Depth limits the transmit and receive FIFO depth to 16 or 256 when FIFO is enabled. When FIFO is not enabled, the value of FIFO depth parameter is considered to be 0. A FIFO depth of 256 should be used because this is the most suitable depth in relation to the flash memory page size.
•The valid values for the FIFO Depth option in this mode are 16 or 256 when FIFO is enabled through Enable FIFO parameter.
When Enable FIFO is 0 and no FIFO is included in the core. Data transmission occurs through the single transmit and receive register. When FIFO Depth is 16 or 256, the transmit or receive FIFO is included in the design with a depth of 16 or 256 elements. The width of the transmit and receive FIFO is configured with the Transaction Width option.
The AXI Quad SPI core supports continuous transfer mode. When configured as master, the transfer continues until the data is available in the transmit register/FIFO. This capability is provided in both manual and automatic slave select modes. As an example, during the page read command, the command, address, and number of data beats in the DTR must be set equal to the same number of data bytes intended to be read by the SPI memory.
When the core is configured as a slave, if the slave select line (SPISEL) goes High (inactive state) during the data element transfer, the current transfer is aborted. If the slave select line goes Low, the aborted data element is transmitted again. The slave mode of the core is allowed only in the standard SPI mode.