Hello TJ
Yes, the S4 is able to emulate the National Semi. 27C256B device. You will need the "S4 8 bit (EPROM) lib. V3.00" which is available from our website
here. You should already have the S4 emulation lead or EMULEAD.
Emulating is as simple as loading your code into the S4 RAM either from a PC or by loading from a PROM, then hitting the EMU key to begin emulation. This is assuming that you have already connected up the EMU lead and have the National 27C256B device selected from the PROM menu.
Emulation will continue until the ESC key is pressed.
Aditional information on the emulation capabilities of the S4 can be found
here.
Regards
Neil Parker (Dataman)