Freescale Semiconductor MCF51QE128RM Flash Configuration Register Fcnfg, Fopt Field Descriptions

Chapter 4 Memory

The FOPT register is loaded from the flash configuration field (see Section 4.2.1) during the reset sequence, indicated by F in Figure 4-4.

The security feature in the flash module is described in Section 4.5.5, “Security”.

R

W

Reset

7	6		5	4	3	2	1	0
	KEYEN		0	0	0	0		SEC
F		F	0	0	0	0	F		F

		Figure 4-4. Flash Options Register (FOPT)
		Table 4-10. FOPT Field Descriptions
Field		Description
7–6	Backdoor Key Security Enable Bits. The KEYEN[1:0] bits define the enabling of backdoor key access to the
KEYEN	flash module.
	00	Disabled
	01	Disabled (Preferred KEYEN state to disable Backdoor Key Access)
	10	Enabled
	11	Disabled
5–2	Reserved, should be cleared.
1–0	Flash Security Bits. The SEC[1:0] bits define the security state of the MCU. If the flash module is unsecured
SEC	using backdoor key access, the SEC[1:0] bits are forced to the unsecured state.
	00	Unsecured
	01	Unsecured
	10	Secured
	11	Unsecured

4.4.2.3Flash Configuration Register (FCNFG)

The FCNFG register gates the security backdoor writes.

KEYACC is readable and writable while all remaining bits read 0 and are not writable. KEYACC is only writable if KEYEN is set to the enabled state (see Section 4.4.2.2, “Flash Options Register (FOPT and NVOPT)”).

NOTE

Flash array reads are allowed while KEYACC is set.

R

W Reset

7	6	5	4	3	2	1	0
0	0	KEYACC	0	0	0	0	0
0	0	0	0	0	0	0	0

Figure 4-5. Flash Configuration Register (FCNFG)

MCF51QE128 MCU Series Reference Manual, Rev. 3

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