parallel communication is possible using arduino you need to use the  ports for example port A and then a rx tx pins.

[![code setting up ports][1]][1]


[![transmit  function][2]][2]


Here we set up the two ports DDRA and DDRC to be output ports by using the   mask B11111111; We set the interrupt pin to port 44 and set it is an output and we set the receive pin to be 45 and an input.
Then we call transmit in the loop. Where we then set port A  and port C to equal i++ and I respectively . And then toggle the signal to say we have transmitted a new message. This will get picked up by the Slave-input.

Slave input
[![slave input  code][3]][3]
[![blink  function for interrupt][4]][4]

Here we  set up the two ports DDRA and DDRC to be input ports by using the   mask B00000000;
 We then set the  baud  rate as 19200 which matches the   sate set by the master

 Here we set the interrupt to be 5 which is pin 18 and tell it to call blink on an interrupt.
 We then read the values from PORTA and PORTC and then we output it to the serial monitor screen. We also send  back the  acknowledgement of receipt to the master using  pin 45




  [1]: https://i.sstatic.net/IJP1B.png
  [2]: https://i.sstatic.net/8DQAy.png
  [3]: https://i.sstatic.net/8AW3y.png
  [4]: https://i.sstatic.net/gw9Cj.png