80C186EB/80C188EB Microprocessor User's Manual - CEUNES

OVERVIEW OF THE 80C186 FAMILY ARCHITECTUREDisplacement(Rate)+BaseRegisterEAHigh AddressAge StatusRateVac SickDept DivEmployeeDisplacement(Rate)+Base RegisterEAAge StatusRateVac SickDept DivEmployeeLow AddressA1019-0AFigure 2-16. Accessing a Structure with Based AddressingWith indexed addressing, the effective address is calculated by summing a displacement and thecontents of an index register (SI or DI, see Figure 2-17). Indexed addressing is often used to accesselements in an array (see Figure 2-18). The displacement locates the beginning of the array,and the value of the index register selects one element. If the index register contains 0000H, theprocessor selects the first element. Since all array elements are the same length, simple arithmeticon the register can select any element.2-32