I use a Dataman S4 for 27C256, and it is universal so it programs 28C256 also. The only difference anyway is that 27C256 is EPROM. It's pretty expensive though, 600 dollars or something. The -15, -25 is probably the access time, 15 = 150 ms and 25 = 250 ms. I use 150 ms and that works ok.

/ Jsr