Cypress AN82156 has an example of the parallel input to Datapath (see example #5 in code provided)
Many thanks for the pointer to the app note. I have already used this and have had PI working in the past, but only in fixed mode. That is to say that the SRCA input to the ALU is always PI for every instruction.
The DYN PI bit in CFG15-14 should allow each individual instruction to choose whether SRCA comes from the PI or A0 register, and it is this feature that I need for my design.
The link that I referenced indicates that DYN PI does not work for PSoC5 but should for PSoC3 and PSoC5LP. Sadly, the DYN PI option appears to be greyed out in the Datapath Tool, and I assume this is because the tool believes that my design may be targeted at a PSoC5 device. I'm trying to figure out how to overcome this.
Looking at my code again, I see that the 'defines that I mentioned are only implemented for simulation, so that theory is a red herring.
Can anyone confirm that they have DYN PI working on PSoC5LP?
OK, I think I have just found the answer just in case it helps anyone else.
If the PI DYN bit is greyed out in the Datapath Tool, then right click on the grey box and you are given the option to "Enable Bit". This results in the PI DYN bit becoming available, and the PI SEL bit then becomes greyed (as these options are mutually exclusive).
Thanks for anyone that has looked into this problem.