mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 631

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

17.4.2
17.4.2.1
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 MCU enters active BDM mode the BDM firmware lookup tables and the BDM registers become
visible in the local memory map between addresses $FF00 and $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 $BF00 and $BFFF if the PPAGE register contains value of
$FF.
Freescale Semiconductor
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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.
Memory Map Scheme
CPU and BDM Memory Map Scheme
MC9S12XDP512 Data Sheet, Rev. 2.17
Chapter 17 Memory Mapping Control (S12XMMCV2)
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