MC9S12XD256MAL Datasheet, PDF (801/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 21 External Bus Interface (S12XEBIV2)
21.5.2 Emulation Modes
In emulation mode applications, the development systems use a custom PRU device to rebuild the
single-chip or expanded bus functions which are lost due to the use of the external bus with an emulator.
Accesses to a set of registers controlling the related ports in normal modes (refer to SoC section) are
directed to the external bus in emulation modes which are substituted by PRR as part of the PRU. Accesses
to these registers take a constant time of 2 cycles.
Depending on the setting of ROMON and EROMON (refer to S12X_MMC section), the program code
can be executed from internal memory or an optional external emulation memory (EMULMEM). No wait
state operation (stretching) of the external bus access is done in emulation modes when accessing internal
memory or emulation memory addresses.
In both modes observation of the internal operation is supported through the external bus (internal
visibility).
MC9S12XDP512 Data Sheet, Rev. 2.21
Freescale Semiconductor
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