Hi,
The '165 is an 8bit parallel in/serial out shift register. If reading it with PBP you use the Shiftin command. I mention this because you say you're trying see the 8bit serial output which to me sounds as if your trying to use with Shiftout. The DS input of the chip is a serial input but there's no way to "see" the data being shifted in, it's used to shift data "thru" the device when cascading several '165's.

OK, the PL input is what "loads" the 8 bits of data (D0-D7) into the internal shift register. CP and CE are the two clock inputs, CP is active high, CE is active low.

This datasheet has a pretty good description of how it works.

/Henrik.