Freescale Semiconductor MCF51QE128RM manual Flash Protection Register Fprot and Nvprot, FPS Fpopen

Chapter 4 Memory

		Table 4-11. FCNFG Field Descriptions
Field		Description
7–6	Reserved, should be cleared.
5	Enable Security Key Writing
KEYACC	0	Writes to the flash block are interpreted as the start of a command write sequence.
	1	Writes to the flash block are interpreted as keys to open the backdoor.
4–0	Reserved, should be cleared.

4.4.2.4Flash Protection Register (FPROT and NVPROT)

The FPROT register defines which flash sectors are protected against program or erase operations. FPROT bits are readable and writable as long as the size of the protected flash memory is being increased. Any write to FPROT that attempts to decrease the size of the protected flash memory is ignored.

During the reset sequence, the FPROT register is loaded from the flash protection byte in the flash configuration field (see Section 4.2.1), indicated by F in Table 4-6. To change the flash protection loaded during the reset sequence, the flash sector containing the flash configuration field must be unprotected. Then, the flash protection byte must be reprogrammed.

Trying to alter data in any protected area in the flash memory results in a protection violation error and FSTAT[FPVIOL] is set. The mass erase of the flash array is not possible if any of the flash sectors contained in the flash array are protected.

R

W

Reset

7	6	5	4	3	2	1	0
			FPS				FPOPEN
F	F	F	F	F	F	F	F

		Figure 4-6. Flash Protection Register (FPROT)
		Table 4-12. FPROT Field Descriptions
Field		Description
7–1	Flash Protection Size. With FPOPEN set, the FPS bits determine the size of the protected flash address range
FPS	as shown in Table 4-13.
0	Flash Protection Open
FPOPEN	0	Flash array fully protected.
	1	Flash array protected address range determined by FPS bits.

Table 4-13. Flash Protection Address Range

FPS	FPOPEN	Protected Address Range	Protected
		Relative to Flash Array Base	Size
—	0	0x0_0000–0x1_FFFF	128 Kbytes

MCF51QE128 MCU Series Reference Manual, Rev. 3

74 Freescale Semiconductor

Get the latest version from freescale.com