z8f083a ZiLOG Semiconductor, z8f083a Datasheet - Page 123

• Manufacturer Part Number: z8f083a
• Description: High-performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

.h Code Protection using Flash Controller
PS026308-1207
Table 69. Flash Code Protection using the Flash Option Bits
At reset, the Flash controller is locked to prevent accidental program or erasure of the
Flash memory. To program or erase the Flash memory, first write the target page to the
page select register. Unlock the Flash controller by making two consecutive writes to the
Flash control register with the values
must be rewritten with the same page previously stored there. If the two page select writes
do not match, the controller reverts to a Locked state. If the two writes match, the selected
page becomes active. For details, see
After unlocking a specific page, you enable either page program or erase. Writing the
value
protected. Any other value written to the Flash control register locks the Flash controller.
Mass erase is not allowed in the user code, but is allowed through the debug port.
After unlocking a specific page, you also write to any byte on that page. After a byte is
written, the page remains unlocked, allowing for subsequent writes to other bytes on the
same page. Further writes to the Flash control register causes the active page to revert to a
Locked state.
Sector Based Flash Protection
The final protection mechanism is implemented on a per-sector basis. The Flash memories
of Z8 Encore! devices are divided into maximum number of eight sectors. A sector is one-
eighth of the total size of the Flash memory, unless this value is smaller than the page size,
in which case the sector and page sizes are equal. On the Z8 Encore! F083A Series
devices, the sector size is varied according to the
The sector protect register controls the protection state of each Flash sector. This register
is shared with the page select register. It is accessed by locking the Flash controller and
writing the command byte
protect register.
The sector protect register is initialized to 0 on reset, putting each sector into an
unprotected state. When a bit in the sector protect register is written to 1, the
corresponding sector is no longer be written or erased. After setting a bit in the sector
protect register, the bit cannot be cleared by you.
FHSWP
0 or 1
0
95H
causes a page erase only if the active page resides in a sector that is not
FWP
0
1
Flash Code Protection Description
Programming and erasing disabled for all Flash program memory.
In user code programming, page erase, and mass erase are all
disabled. Mass erase is available through the On-Chip Debugger.
Programming, page erase, and mass erase are enabled for all the
Flash program memory.
5EH
. The next write to the page select register targets the sector
73H
Figure
and
16.
8CH
Table 68
, sequentially. The page select register
on page 108.
Z8 Encore!
Product Specification
®
F083A Series
Flash Memory
111