I am designing usin an xc9500 Xilinx PLD and i observed some strange behavior, wondering if anyone can confirm or deny.
It appears that a macrocell is used for each output pin (or bidirectional). I get a summery like this:
Total Macrocells Available 216 Registered Macrocells 124 Non-registered Macrocells driving I/O 48
My design has about 120 macrocells, and these 48 dirving are bothering me. Why does it need a macrocell for the I/O. I put the chip in low power output mode, hoping that would free them up, but no luck.
Mike D