Use pointer arithmetic, as
uint8 * Mypointer;
Assign your starting address to it and read from as
Sum += *(Mypointer++);
Easier than I expected :)
This covers the organization of memory, and name of pointers to it -
http://www.cypress.com/documentation/application-notes/an89610-psoc-4-and-psoc-5lp-arm-cortex-code-optimization AN89610 - PSoC® 4 and PSoC 5LP ARM Cortex Code Optimization
cydevice.h contains key base addresses. Auto generated, in workspace explorer.