i,m using AT89c52, but 89C5115 and 87C51FA have PCA, and these two devices are similar to AT89c51 which is also exact the same like AT89c52 , so i thinking they are the same as they have the same series.

so now if AT89c52 don`t have PCA, means i have to use another register to run the stepper motors at full speed, so what register you suggest.

but also i have so,e problem with IT registers,for example, when i move 10H into IPL0 to Set Serial Interrupt Priority, it give me error A45: undefined sympol i will be thank full to you if you can help mein this case.
(mov IPL0, #10H)
(mov IPH0, #00H)

Albarkani