Simple Serial Config?

i am working on a CNC controller
im using an ARM and a usb to rs232 chip

i cant go in to to much detail on it but basically i need EMC to send threw a serial port a command for every step and listen and react to bumper commands
example

TX:
X_Forward
X_Backwards
Y_Forward
Y_Backwards
Z_Up
Z_Down

RX:
X_Bumper_front
exc... exc...
also i can do it in non ascii like numbers from 0-255

... also any other commands like engaging the router mill or speed control would be grate but the basics are all i need first i can program the microcontroller and work the hardware around this but i have no experience with EMC

any preexisting serial configuration that works step to step (i cant have it store any information) that already exists will work i can open the config adn figure out the serial commands

if there is one already configured with EMC give me the name

thank you all!
credit will be given on the final product to the one who can help

I think its unlikely to work because of jitter induced by the timing of the USB-Serial. Step motors need accurately spaced steps at a high rate. The USB parts precludes accurate step spacing and the serial
part prevents high rates. Certainly buffered USB interfaced step generators can generate accurate and high speed steps but in this case the USB peripheral generates the step timing, not EMC, and EMC is not designed to work with buffered devices.

Its probably possible to make a pure serial step motor interface work with EMC at relatively low speeds,
for example if you sent a single byte with up to 4 sets of up/down step commands encoded in the bits, and the uProc did the step width timing, a single byte sent every base thread period would allow step rates up to about 10 KHz at 115200 baud. Each Transmitted byte could cause the uProc to echo a byte for limit switches etc. Note that this would not work if any kind of USB adapter was used, as it would add too much jitter to the data stream.

im using a ATMEGA8U2 with a custom firmware to act alone as an extremely high speed usb to RS232 with extremely limited lag taking advantage of full USB2.0 speeds
speed of run at this point is something i can work out later as my final setup will take advantage of USB 3.0 and LAN but for now all i need is as previously stated

i can PROBABLY have it store small bits of data
example
Move_Z_forward
200

moving 200 steps forward but i cant have it store mutables because of limited space for example i cant have both X and Y moving at the same time for any one command

but out of curiosity is there a low cost USB driver you recommend?

im driving 5.5 amp steppers at 25V

i have a stepper driver done where its controlled with one pulse per step, a 1 or 0 for direction, a 1 or 0 for full/half step (not required can be hardware), than home 1/0(not required)
if there is a controller without a stepper driver that can take advantage of this ^ via USB that would be wonderful ... if not any 5A controller will do
if i cant get my current system to work piggybacking it with a commercial controller might be an option

you know what
never mind im going to go ahead of do a parallel port controller until i can figure out a better way to use the ARM to do this

can you link me to how it is driven from the parallel port?
like a pinout and description or something?