mc9s12uf32 Freescale Semiconductor, Inc, mc9s12uf32 Datasheet - Page 82

• Manufacturer Part Number: mc9s12uf32
• Description: System Chip Guide V01.05
• Manufacturer: Freescale Semiconductor, Inc

System on a Chip Guide — 9S12UF32DGV1/D V01.05
The pins associated with Port E bits 6, 5, 3, and 2 cannot be configured for their alternate functions IPIPE1,
IPIPE0, LSTRB, and R/W while the MCU is in single chip modes In single chip modes, the associated
control bits PIPOE, LSTRE and RDWE are reset to zero. Writing the opposite value into these bits in
single chip mode does not change the operation of the associated Port E pins.
Port E, bit 4 can be configured for a free-running ECLK output by clearing NECLK=0. Typically the only
use for an ECLK output while the MCU is in single chip modes would be to get a constant speed clock for
use in the external application system.
4.2.2.2 Special Test Mode
In expanded wide modes, Ports A and B are configured as a 16-bit multiplexed address and data bus and
Port E provides bus control and status signals. In special test mode, the write protection of many control
bits is lifted so that they can be thoroughly tested without needing to go through reset.
4.2.2.3 Special Peripheral Mode
This mode is intended for Motorola factory testing of the MCU. In this mode, the CPU is inactive and an
external (tester) bus master drives address, data and bus control signals in through Ports A, B and E. In
effect, the whole MCU acts as if it was a peripheral under control of an external CPU. This allows faster
testing of on-chip memory and peripherals than previous testing methods. Since the mode control register
is not accessible in peripheral mode, the only way to change to another mode is to reset the MCU into a
different 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.
4.3 Internal Visibility
Internal visibility is available when the MCU is operating in expanded wide modes or special test modes.
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 the ECLK, R/W, and LSTRB are configured as bus control outputs and
internal visibility is off (IVIS=0), ECLK 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.
4.4 Security
The device will make available a security feature preventing the unauthorized read and write of the
memory contents. This feature allows:
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