EZ80F91MCU Datasheet, PDF (134/396 Pages) Zilog, Inc. – eZ80Acclaim-TM Flash Microcontrollers

eZ80F91 MCU
Product Specification
115
Flash Write/Erase Protection Register
The Flash Write/Erase Protection register prevents accidental Write or Erase
operations. The protection is limited to a resolution of eight 32 KB blocks. Setting a
bit to 1 protects that 32 KB block of Flash memory from accidental Writes or
erases. The default upon RESET is for all Flash memory blocks to be protected.
The WP pin works in conjunction with FLASH_PROT[0] to protect the lowest
block (also called the Boot Block) of Flash memory. If either the WP is held
asserted or FLASH_PROT[0] is set, the Boot Block is protected from Write and
Erase operations.
Note: A protect bit is not available for the information page. The information page is,
however, protected from a MASS ERASE if any pages are protected in
FLASH_PROT or WP is asserted.
Writes to this register are allowed only after it is unlocked via the FLASH_KEY
register. Any attempted Writes to this register while locked will set it to FFh,
thereby protecting all blocks. See Table 40.
Table 40. Flash Write/Erase Protection Register
(FLASH_PROT = 00FAh)
Bit
7
6
5
4
3
2
1
0
Reset
1
1
1
1
1
1
1
1
CPU Access
R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W*
Note: R/W = Read/Write if unlocked, R = Read Only if locked. *Key sequence required to unlock.
Bit
Position
Value Description
[7]
0
BLK7_PROT ₁
Disable Write/Erase Protect on block 38000h to 3FFFFh.
Enable Write/Erase Protect on block 38000h to 3FFFFh.
[6]
0
BLK6_PROT ₁
Disable Write/Erase Protect on block 30000h to 37FFFh.
Enable Write/Erase Protect on block 30000h to 37FFFh.
[5]
0
BLK5_PROT ₁
Disable Write/Erase Protect on block 28000h to 2FFFFh.
Enable Write/Erase Protect on block 28000h to 2FFFFh.
[4]
0
BLK4_PROT ₁
Disable Write/Erase Protect on block 20000h to 27FFFh.
Enable Write/Erase Protect on block 20000h to 27FFFh.
Note: The lower 32 KB block (00000h to 07FFFh—BLK0) is called the Boot Block and can be
protected using the external WP pin.
PS019209-0504
PRELIMINARY
Flash Memory