PC912XDP512F0MPVR datasheet(1225/1348 Pages) FREESCALE

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Chapter 29 128 Kbyte Flash Module (S12XFTX128K1V1)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

1227

29.5

Operating Modes

29.5.1

Wait Mode

If a command is active (CCIF = 0) when the MCU enters wait mode, the active command and any buffered

command will be completed.

The Flash module can recover the MCU from wait mode if the CBEIF and CCIF interrupts are enabled

(see Section 29.8, “Interrupts”).

29.5.2

Stop Mode

If a command is active (CCIF = 0) when the MCU enters stop mode, the operation will be aborted and, if

the operation is program or erase, the Flash array data being programmed or erased may be corrupted and

the CCIF and ACCERR ﬂags will be set. If active, the high voltage circuitry to the Flash memory will

immediately be switched off when entering stop mode. Upon exit from stop mode, the CBEIF ﬂag is set

and any buffered command will not be launched. The ACCERR ﬂag must be cleared before starting a

command write sequence (see Section 29.4.1.2, “Command Write Sequence”).

NOTE

As active commands are immediately aborted when the MCU enters stop

mode, it is strongly recommended that the user does not use the STOP

instruction during program or erase operations.

29.5.3

Background Debug Mode

In background debug mode (BDM), the FPROT register is writable. If the MCU is unsecured, then all

Flash commands listed in Table 29-18 can be executed. If the MCU is secured and is in special single chip

mode, only mass erase can be executed.

29.6

Flash Module Security

The Flash module provides the necessary security information to the MCU. After each reset, the Flash

module determines the security state of the MCU as deﬁned in Section 29.3.2.2, “Flash Security Register

(FSEC)”.

The contents of the Flash security byte at 0x7F_FF0F in the Flash Conﬁguration Field must be changed

directly by programming 0x7F_FF0F when the MCU is unsecured and the higher address sector is

unprotected. If the Flash security byte is left in a secured state, any reset will cause the MCU to initialize

to a secure operating mode.

29.6.1

Unsecuring the MCU using Backdoor Key Access

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 Section 29.3.2.2, “Flash Security Register (FSEC)”) and

the KEYACC bit is set, a write to a backdoor key address in the Flash memory triggers a comparison

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