Freescale 9S12 Shared I/Os


I have a requirement to use bits 6 and 7 of Port J on a Freescale MC9S12DG128CPVE device as an IIC peripheral. It is not clear to me whether or not, in addition to simply "turning on" the peripheral via the IBEN bit in the IIC Bus Control Register (IBCR), manual configuration of bits 6 and 7 on port J is required.

Specifically, I have the following questions on the configuration for these bits:

  1. Do I need to do something to select these bits for the IIC module as opposed to GPIO, CAN or whatever other purposes these bits can be used for?
  2. Do I need to set the DDRJ (data direction register)?
  3. Do I need to set the RDRJ (reduced drive register)?
  4. Do I need to set the PERJ (pull device enable register)?
  5. Do I need to set the PPSJ (polarity select register)?
  6. Do I need to set the PIFJ (interrupt flag register)?
  7. Do I need to set the PPSJ (polarity select register)?

As I understand the PIM Block guide and the information about "precedences" for this port, simply setting the IBEN bit in the IBCR is all I need to do, provided no other peripheral for the port (e.g., CAN4) is enabled. Is this correct?

Randy Yates 
Digital Signal Labs 
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