cjcarpenter cjcarpenter

RS08 Design Decisions -- Register Packing

Discussion created by cjcarpenter cjcarpenter on Mar 25, 2007
Latest reply on Mar 28, 2007 by cjcarpenter cjcarpenter

In looking at the RS08 configuration registers, you can't help but notice that they _could_ have been much more tightly packed.    For example:  the ICSC1 and ICSC2 registers occupy 16 bits of RAM  address space at $0014 and $0015 -- but only 5 of these sixteen bits are actually used.  Similarly, locations $0017 and $0018 could clearly be combined into a single byte -- with two bits to spare.

Does anyone know why Freescale chose to abandon so many bit addresses in low RAM, rather than implementing them and allowing their use as flags?  I would think that the real estate savings from not doing this would be marginal.