MC9S12XD256MAL Datasheet, PDF (672/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 18 Memory Mapping Control (S12XMMCV3)
• Normal expanded mode
The external bus interface is configured as an up to 23-bit address bus, 8 or 16-bit data bus with
dedicated bus control and status signals. This mode allows 8 or 16-bit external memory and
peripheral devices to be interfaced to the system. The fastest external bus rate is half of the internal
bus rate. An external signal can be used in this mode to cause the external bus to wait as desired by
the external logic.
• Emulation expanded mode
Tool vendors use this mode for emulation systems in which the user’s target application is normal
expanded mode.
• Special test mode
This mode is an expanded mode for factory test.
18.4.2 Memory Map Scheme
18.4.2.1 CPU and BDM Memory Map Scheme
The BDM firmware lookup tables and BDM register memory locations share addresses with other
modules; however they are not visible in the memory map during user’s code execution. The BDM
memory resources are enabled only during the READ_BD and WRITE_BD access cycles to distinguish
between accesses to the BDM memory area and accesses to the other modules. (Refer to BDM Block
Guide for further details).
When the MCU enters active BDM mode, the BDM firmware lookup tables and the BDM registers
become visible in the local memory map in the range 0xFF00-0xFFFF (global address 0x7F_FF00 -
0x7F_FFFF) and the CPU begins execution of firmware commands or the BDM begins execution of
hardware commands. The resources which share memory space with the BDM module will not be visible
in the memory map during active BDM mode.
Please note that after the MCU enters active BDM mode the BDM firmware lookup tables and the BDM
registers will also be visible between addresses 0xBF00 and 0xBFFF if the PPAGE register contains value
of 0xFF.
MC9S12XDP512 Data Sheet, Rev. 2.21
672
Freescale Semiconductor