I haven't used the HCPL 7860, but I have used Microwire & SPI devices with PBP.

PBP's SHIFTOUT / SHIFTIN commands are used for Microwire & SPI communications.

Here's a few examples;

SPI:
http://www.microengineeringlabs.com/...1/pbp/spix.bas

Microwire:
http://www.microengineeringlabs.com/...x1/pbp/mwx.bas