Need advice for electromechanical system modeling

I need to design microcontroller based system (will be 8052) to control printing machine. the system will replace old system based on group of timers control Heater, pressure piston, table moving neumatic arm..etc .
I need first to model the system to clearly understand the relation between system components. I need advice which tool is better and simple Simulink, VHDL, proteus ... or what for this specific case

better to export to a second micro as printing slave micro from a serial input
use the second micro as serial to lpt common {easy libs pre made..both serial and parallel}

this way you can
1} debug the serial { or second micro using lpt on pc foldback}
2} print without impacting your control systems vectors and pins etc the control mcu core uses ...

8051 /2 exports 115k easy on one pin +gnd to another 'printer' mcu ...
if you dont need hi speed print >115k baud then serial export to printing core is better

just my opinion

:-(

dont try to do everything using one core

just external tasks must use another core

free's from a long task a dedicated core in control of crytical stuff
serial can be sent on the fly using the h/w uart on 8052

as serial is easier to spool to a printing core...

8052 has no such parallel uart {sepearate core in essance}