Access odd memory locations without hardware


Posted on Jul 29, 2012

Some RISC controllers, like the NEC V850 family, use an internal 32-bit architecture with an external 16-bit bus. The architecture also allows interfaces with 8-bit memories. However, with 8-bit memories, accesses to and from odd locations automatically access the higher-order byte. Thus, you would need external transceivers to access both even and odd locations. However, you can `trick` the processor and thereby save the space and cost associated with the external transceivers. Like everything else in life, the method doesn`t come freethe price you pay is execution time.



The idea (Figure 1) is fairly simple: Connect the memory data bus to the least-significant bit (D0 to D7) of the µC. Then, connect the memory-address bus to the µC without using A0, so that the memory never sees an odd address. Thus, addressing the




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