3.3.16.3 Address Generation Units and DSP Class Instructions

The Y AGU and Y memory data path are used in concert with the X RAGU by the DSP class of instructions to provide two concurrent data read paths. For example, the MAC instruction can simultaneously fetch two operands to be used in the next multiplication.

DSP class of instructions may use any W-reg (except W15) for either X or Y address space accesses, unlike previous devices. Any data write performed by a DSP class instruction takes place in the combined X and Y data space and the write occurs across the X-bus. Consequently, the data can be written to any address regardless of where the EA is directed.

The Y AGU only supports Post-Modification Addressing modes associated with the DSP class of instructions. The Y AGU also supports Modulo Addressing for automated circular buffers. All other (MCU) class instructions can access the Y data address space through the X AGU when it is regarded as part of the composite linear space.