MAX7219, SPI capable/Timing question?
The datasheet seems pretty clear. The 7221 has an SPI compliant /CS input, whereas the 7219 takes any 16 bits it sees:


  For the MAX7219, serial data at DIN, sent in 16-bit
  packets, is shifted into the internal 16-bit shift register
  with each rising edge of CLK regardless of the state of
  LOAD.


For the 7221 it says:


  LOAD/CS must go high concurrently with or after the
  16th rising clock edge, but before the next rising clock
  edge


That just means that you must take LOAD/CS high after sending 16 bits and before any 17th bit is sent.

So, you can safely talk to the 7219 via SPI if it is the only device on that bus, i.e. you don't need a /CS signal, or if at least the clock line is dedicated for the 7219.