The synchronous serial port interface (SPI) can be used for system debugging. It can also be
used for in-system programming for the flash memory within the module. SPI interface
uses the SPI_MOSI, SPI_MISO, SPI_CSB and SPI_CLK pins. Testing points for the SPI
interface are reserved on board in case that the firmware shall be updated during
The module operates as a slave and thus SPI_MISO is an output of the module.
SPI_MISO is not in high-impedance state when SPI_CSB is pulled high. Instead, the
module outputs 0 if the processor is running and 1 if it is stopped. Thus the module
should NOT be connected in a multi-slave arrangement by simple parallel connection
of slave SPI_MISO lines.