In case of high precision devices with just a simple SPI interface
for control and data, the effective data rate can be significatly
lower than the SPI clock, and more importantly there isn't any relation
between the two clock domain.
The rate is defined by a SOT (start of transfer) generator, which
initiates a SPI transfer. Taking the fact that the generator runs
on system clock (100 MHz), and the device can require smaller rate (in kHz domain),
the 7 bit dac_datarate register is just too small.
Therefor increasing to 16 bit.
This core can be used in conjunction with the SPI_ENGINE, will work
as an offload module, forwarding a data stream to the SPI excecution,
received from a DMA.
Rejeesh Kutty
Istvan Csomortani