C167CS-4RM datasheet(73/517 Pages) INFINEON

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C167CS

Derivatives

The Central Processing Unit (CPU)

User’s Manual

4-23

V2.0, 2000-07

The DPP registers are implicitly used, whenever data accesses to any memory location

are made via indirect or direct long 16-bit addressing modes (except for override

accesses via EXTended instructions and PEC data transfers). After reset, the Data Page

Pointers are initialized in a way that all indirect or direct long 16-bit addresses result in

identical 18-bit addresses. This allows to access data pages 3 … 0 within segment 0 as

shown in Figure 4-6. If the user does not want to use any data paging, no further action

is required.

Data paging is performed by concatenating the lower 14 bits of an indirect or direct long

16-bit address with the contents of the DPP register selected by the upper two bits of the

16-bit address. The contents of the selected DPP register specify one of the

1024 possible data pages. This data page base address together with the 14-bit page

offset forms the physical 24-bit address (selectable part is driven to the address pins).

In case of non-segmented memory mode, only the two least significant bits of the

implicitly selected DPP register are used to generate the physical address. Thus,

extreme care should be taken when changing the content of a DPP register, if a non-

segmented memory model is selected, because otherwise unexpected results could

occur.

In case of the segmented memory mode the selected number of segment address bits

(via bitfield SALSEL) of the respective DPP register is output on the respective segment

address pins of Port 4 for all external data accesses.

A DPP register can be updated via any instruction, which is capable of modifying an SFR.

Note: Due to the internal instruction pipeline, a new DPP value is not yet usable for the

operand address calculation of the instruction immediately following the

instruction updating the DPP register.

Bit

Function

DPPxPN

Data Page Number of DPPx

Specifies the data page selected via DPPx. Only the least significant two

bits of DPPx are significant, when segmentation is disabled.

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