MC9S12KG128 Datasheet, PDF (538/600 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 18 Multiplexed External Bus Interface (MEBIV3)
mode. Background debugging should not be used while the MCU is in special peripheral mode as internal
bus conflicts between BDM and the external master can cause improper operation of both functions.
18.4.4 Internal Visibility
Internal visibility is available when the MCU is operating in expanded wide modes or emulation narrow
mode. It is not available in single-chip, peripheral or normal expanded narrow modes. Internal visibility is
enabled by setting the IVIS bit in the MODE register.
If an internal access is made while E, R/W, and LSTRB are configured as bus control outputs and internal
visibility is off (IVIS=0), E will remain low for the cycle, R/W will remain high, and address, data and the
LSTRB pins will remain at their previous state.
When internal visibility is enabled (IVIS=1), certain internal cycles will be blocked from going external.
During cycles when the BDM is selected, R/W will remain high, data will maintain its previous state, and
address and LSTRB pins will be updated with the internal value. During CPU no access cycles when the
BDM is not driving, R/W will remain high, and address, data and the LSTRB pins will remain at their
previous state.
NOTE
When the system is operating in a secure mode, internal visibility is not
available (i.e., IVIS = 1 has no effect). Also, the IPIPE signals will not be
visible, regardless of operating mode. IPIPE1–IPIPE0 will display 0es if
they are enabled. In addition, the MOD bits in the MODE control register
cannot be written.
18.4.5 Low-Power Options
The MEBI does not contain any user-controlled options for reducing power consumption. The operation
of the MEBI in low-power modes is discussed in the following subsections.
18.4.5.1 Operation in Run Mode
The MEBI does not contain any options for reducing power in run mode; however, the external addresses
are conditioned to reduce power in single-chip modes. Expanded bus modes will increase power
consumption.
18.4.5.2 Operation in Wait Mode
The MEBI does not contain any options for reducing power in wait mode.
18.4.5.3 Operation in Stop Mode
The MEBI will cease to function after execution of a CPU STOP instruction.
MC9S12KG128 Data Sheet, Rev. 1.15
538
Freescale Semiconductor