ez80f91 ZiLOG Semiconductor, ez80f91 Datasheet - Page 110

• Manufacturer Part Number: ez80f91
• Description: Ez80 Acclaimplus!? Connectivity Assp Ez80f91 Assp
• Manufacturer: ZiLOG Semiconductor

PS027001-0707
Information Page Characteristics
Flash Control Registers
As noted earlier, the information page is not accessible using memory access instructions
and must be accessed via the FLASH_DATA I/O register. The Flash Page Select Register
contains a bit which selects the information page for I/O access.
There are two ways to erase the information page. You must set the FLASH_PAGE regis-
ter(0x00FC) bit7(INFO_EN) and then you execute either a MASS ERASE (which also
erases the entire main Flash memory array) operation or a PAGE ERASE operation.
The Flash Control Register interface contains all the registers used in Flash memory. The
definitions in this section describe each register.
Flash Key Register
Writing the two-byte sequence B6h, 49h in immediate succession to this register unlocks
the Flash Divider and Flash Write/Erase Protection registers. If these values are not
written by consecutive CPU I/O Writes (I/O reads and memory Read/Writes have no
effect), the Flash Divider and Flash Write/Erase Protection registers remain locked. This
prevents accidental overwrites of these critical Flash control register settings. Writing a
value to either the Flash Frequency Divider Register or the Flash Write/Erase Protection
Register automatically relocks both of the registers. See
Table 35. Flash Key Register
Bit
Reset
CPU Access
Note: W = Write Only.
Bit
Position
[7:0]
FLASH_KEY
Value Description
B6h,
49h
Sequential Write operations of the values B6h, 49h to this
register will unlock the Flash Frequency Divider and Flash
Write/Erase Protection registers.
W
7
0
(FLASH_KEY = 00F5h)
W
6
0
W
5
0
W
4
0
Table
W
3
0
35.
Product Specification
W
2
0
eZ80F91 ASSP
W
1
0
Flash Memory
W
0
0
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