S12G Memory Map Controller (S12GMMCV1)
MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 267
The page value for the program page window is stored in the PPAGE register. The value of the PPAGE
register can be read or written by normal memory accesses as well as by the CALL and RTC instructions.
Control registers, vector space and parts of the on-chip memories are located in unpaged portions of the
64KB local CPU address space.
The starting address of an interrupt service routine must be located in unpaged memory unless the user is
certain that the PPAGE register will be set to the appropriate value when the service routine is called.
However an interrupt service routine can call other routines that are in paged memory. The upper 16KB
block of the local CPU memory space (0xC000–0xFFFF) is unpaged. It is recommended that all reset and
interrupt vectors point to locations in this area or to the other unmapped pages sections of the local CPU
memory map.
Expansion of the BDM Local Address Map
PPAGE and BDMPPR register is also used for the expansion of the BDM local address to the global
address. These registers can be read and written by the BDM.
The BDM expansion scheme is the same as the CPU expansion scheme.
The four BDMPPR Program Page index bits allow access to the full 256KB address map that can be
accessed with 18 address bits.
The BDM program page index register (BDMPPR) is used only when the feature is enabled in BDM and,
in the case the CPU is executing a firmware command which uses CPU instructions, or by a BDM
hardware commands. See the BDM Block Guide for further details. (see Figure 5-10).
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