My only experience with Horner is their ASCII Basic Coprocessor Module.
HE693ASC900. It has BASIC built in. It appears to the PLC as 8 in/8 out analog. This is how data is passed.
I suspect there may be similarities with the 2 products, but Steve's answer suggests that the BASIC software is external for the DPC165, so just making a connection might not be of much use.
Use Hyperterminal to communicate with the ASC900. Connect with a straight 9 pin cable from Laptop to Port. The ASC900 has Auto baudrate.
Press spacebar to activate.
I don't know if the DPC165 is this smart, but communications should be similar across the range of Horner's products. Try 9600 or 19200, 8 bit, 1 stop, none or odd for parity.
If it has built in BASIC, you should be able to type 'list' [enter] and get a program listing.
If it doesn't have any intelligence built in, then programming is done by reading/writing hex characters, with the formating and compile done in the programmer. In this case, a sucessful connection is pretty much useless, same as connecting to a PLC without a software package - you won't get far.