3.3.16.2 Y Address Generation Unit

The Y data memory space has one AGU that supports data reads from the Y data memory space. The Y memory bus is never used for data writes. The function of the Y AGU and Y memory bus is to support concurrent data reads for DSP class instructions.

The Y AGU can generate an EA within the data space address range 0x0000 to 0xFFFFFF.

The Y AGU timing is identical to that of the X RAGU, in that its EA calculation starts prior to the instruction cycle, using information derived from the prefetched instruction. The EA is presented to the address bus at the beginning of the instruction cycle.

The Y AGU supports Modulo Addressing and Post-Modification Addressing modes for the DSP class of instructions that use it.

Note: The Y AGU does not support data writes. All data writes occur via the X WAGU to the combined X and Y data spaces. The Y AGU is only used during data reads for dual source operand DSP instructions.