upd78f0124hgba1-8et-a Renesas Electronics Corporation., upd78f0124hgba1-8et-a Datasheet - Page 405

• Manufacturer Part Number: upd78f0124hgba1-8et-a
• Description: 8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

CHAPTER 24 FLASH MEMORY
(2) Flash protect command register (PFCMD)
If the application system stops inadvertently due to malfunction caused by noise or program hang-up, an
operation to write the flash programming mode control register (FLPMC) may have a serious effect on the system.
PFCMD is used to protect FLPMC from being written, so that the application system does not stop inadvertently.
Writing FLPMC is enabled only when a write operation is performed in the following specific sequence.
<1> Write a specific value to PFCMD (PFCMD = A5H)
<2> Write the value to be set to FLPMC (writing in this step is invalid)
<3> Write the inverted value of the value to be set to FLPMC (writing in this step is invalid)
<4> Write the value to be set to FLPMC (writing in this step is valid)
This rewrites the value of the register, so that the register cannot be written illegally.
Occurrence of an illegal store operation can be checked by bit 0 (FPRERR) of the flash status register (PFS).
A5H must be written to PFCMD each time the value of FLPMC is changed.
PFCMD can be set by an 8-bit memory manipulation instruction.
RESET input makes PFCMD undefined.
Figure 24-19. Format of Flash Protect Command Register (PFCMD)
Address: FFC0H
After reset: Undefined
W
Symbol
PFCMD
REG7
REG6
REG5
REG4
REG3
REG2
REG1
REG0
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User’s Manual U16962EJ3V0UD