The ICD can run the program from the target CPU step by step, can set a hardware breakpoint or can even update the target firmware without removing it from the circuit. All these useful features are based on the hardware support for In Circuit Programming and Debugging of the PIC16F87X family.
http://www.geocities.com/constantinescuradu/content/docicdw.htm
This is a simple program that can be merged with other sources to allow easy in-circuit debugging.
http://members.home.nl/b.vandam/lonely/pagina8.html
http://www.pjrc.com/tech/8051/board4/schematic.html
shows the logic required to implement an IEEE-1284-compliant parallel port, using the Am29202 RISC processor
http://www.edn.com/archives/1996/011896/02di8.htm
http://www.pjrc.com/tech/8051/board3/schematic.html
68HC11, IR, LCD, motor control
http://handyboard.com/
http://www.stanford.edu/class/ee281/projects/aut2001/digitalcookbook/schematic.pdf