How I control the execution order of the blocks?

Hi, i see this post: https://it.mathworks.com/matlabcentral/fileexchange/64782-can-device-driver-mcp2515-for-arduino-and-raspberry-pi

I have a zedboard with pmod can (https://reference.digilentinc.com/reference/pmod/pmodcan/start). It is built with MCP25625, it is equal to MCP2515 except to the presence of transceiver (equal to register ecc...). Hence, this driver is good also in my case, the only difference is the SPI block driver!

I want to replace the spi block of raspberry with my block.

I have opened the example in package, but i don't understand how you control the execution order of the blocks. Can you tell me? Thank you