PI Control of a DC Motor Using a Peripheral Interface Controller

i need to use PIC 16f877. I need to control the speed of it and also display that speed using a seven segment. any help?

You need a rotary encoder of some kind, perhaps a hall effect sensor and a magnet on the motor shaft. This is the simplest method. If the motor shaft won't experience high temperature or shock forces you can permanently magnetize the shaft with a strong rare earth magnet which won't interfer with the motor shafts physical functionnig, but shock forces or elevated temperature can remove the magnetization in common steels, I've found that heat treating the metal can increase it's retentive properties dramatically.

There is a method to approximate the speed of a running motor by monitoring it's back EMF voltage when it's not being driven, but this is an approximation and if constant drive is required then not practical, the lulls required for establishing a stable back EMF may interfere with the functioning of the device depending on how it's loaded.