As already noted, the 8255 et al were never designed for use with the 8051; are obsolete, and have been obsolete for very many years now!

Back in the early '90s, Waferscale introduced their Microcontroller expansion devices to do for 6811 and 8051 microcontrollers what the 8255 et al hade done for the 8086/88 ten years earlier - and more!

These products now live on as ST's PSM and PSD ranges:
http://www.st.com/stonline/.../index.htm
They integrate memory, IO, and programmable logic.

These days, you can even get them with the 8051 built-in:
http://www.st.com/stonline/...sd_idx.htm

So there really is no excuse to be messing about with an old crock like the 8255!