TMS320C28x Memory Bus (Harvard Bus Architecture)
As with many DSP type devices, multiple busses are used to move data between the memories and
peripherals and the CPU. The C28x memory bus architecture contains a program read bus, data read bus
and data write bus. The program read bus consists of 22 address lines and 32 data lines. The data read
and write busses consist of 32 address lines and 32 data lines each. The 32-bit-wide data busses enable
single cycle 32-bit operations. The multiple bus architecture, commonly termed “Harvard Bus”, enables the
C28x to fetch an instruction, read a data value and write a data value in a single cycle. All peripherals and
memories attached to the memory bus will prioritize memory accesses. Generally, the priority of Memory
Bus accesses can be summarized as follows:
Highest: Data Writes (Simultaneous data and program writes cannot occur on the memory bus.)
Program Writes (Simultaneous data and program writes cannot occur on the memory bus.)
Data Reads
Program Reads (Simultaneous program reads and fetches cannot occur on the memory bus.)
Lowest: Fetches (Simultaneous program reads and fetches cannot occur on the memory bus.)
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