Freescale Semiconductor Demonstration Board for Freescale MC9S12XHY256 Microcontroller DEMO9S12XHY256 DEMO9S12XHY256 Manual De Usuario

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Freescale Semiconductor

The Flash module is not affected if the MCU enters wait mode. The Flash module can recover the MCU
from wait via the CCIF interrupt (see

).

If a Flash command is active (CCIF = 0) when the MCU requests stop mode, the current Flash operation
will be completed before the CPU is allowed to enter stop mode.

The Flash module provides security information to the MCU. The Flash security state is defined by the
SEC bits of the FSEC register (see

). During reset, the Flash module initializes the FSEC

register using data read from the security byte of the Flash configuration field at global address
0x7F_FF0F.

The security state out of reset can be permanently changed by programming the security byte of the Flash
configuration field. This assumes that you are starting from a mode where the necessary P-Flash erase and
program commands are available and that the upper region of the P-Flash is unprotected. If the Flash
security byte is successfully programmed, its new value will take affect after the next MCU reset.

The following subsections describe these security-related subjects:

•

•

•

The MCU may be unsecured by using the backdoor key access feature which requires knowledge of the
contents of the backdoor keys (four 16-bit words programmed at addresses 0x7F_FF00–0x7F_FF07). If
the KEYEN[1:0] bits are in the enabled state (see

), the Verify Backdoor Access Key

command (see

) allows the user to present four prospective keys for comparison to the

Flash Error Interrupt Request

CCIF

CCIE

DFDIF

DFDIE

SFDIF

SFDIE

Flash Command Interrupt Request