Much more information is needed here-
Which 18F MCU would be a start... And, what is the target application? Just one drive, or multiple? And do you want to generate the drive data internally (i.e. robot), or is this an intermediate/translator, etc?
Generating a TTL logic pulse from most any 18F part is trivial. All you have to do is set the TRIS for the pins in question to Output, and then toggle the values for the given port (i.e. PORTE.0 = 1, PORTE.0 = 0). You may also have to disable other peripherals on the port(s) in question- depending on the PIC variant and the port.
You can do that in a timer interrupt routine, or just in the main loop, etc. If you have a motor control PIC (2430 etc) then you have access to some native functionality for HBridge driving, which you could probably use with the 203V just in terms of simplifying step frequency and pulse width.
Are you using a high-level compiler? If so, which?