HD6475348R Datasheet, PDF (60/487 Pages) Hitachi Semiconductor – Single-Chip Microcomputer

3.2.3 Initial Register Values
When the CPU is reset, its internal registers are initialized as shown in table 3-3. Note that the
stack pointer (R7) and base register (BR) are not initialized to fixed values. Also, of the page
registers used in maximum mode, only the code page register (CP) is initialized; the other three
page registers come out of the reset state with undetermined values.
Accordingly, in the minimum mode the first instruction executed after a reset should initialize the
stack pointer. The base register must also be initialized before the short absolute addressing mode
(@aa:8) is used.
In the maximum mode, the first instruction executed after a reset should initialize the stack page
register (TP) and the next instruction should initialize the stack pointer. Later instructions should
initialize the base register and the other page registers as necessary.
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