z16f2811 ZiLOG Semiconductor, z16f2811 Datasheet - Page 270

• Manufacturer Part Number: z16f2811
• Description: High Performance Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS022006-0207
Flash Write/Erase Protection
Programming
OCD or by using the Flash Controller Bypass mode. For more information, see
Bits
The ZNEO Z16F Series provides several levels of protection against accidental program
and erasure of the Flash memory contents. This protection is provided by the Flash
Controller unlock mechanism, the Flash Sector Protect register, and the Flash Write
Protect option bit.
Flash Controller Unlock Mechanism
At Reset, the Flash Controller locks to prevent accidental program or erasure of the Flash
memory. To program or erase the Flash memory, the Flash controller must be unlocked.
After unlocking the Flash Controller, the Flash is programmed or erased. Any value
written by user code to the Flash Command register or Flash Page Select register out of
sequence locks the Flash Controller.
Follow the steps below to unlock the Flash Controller from user code:
1. Write the page to be programmed or erased to the Flash Page Select register.
2. Write the first unlock command
3. Write the second unlock command
Flash Sector Protection
The Flash Sector Protect register is configured to prevent sectors from being programmed
or erased. Once a sector is protected, it cannot be unprotected by user code. The Flash Sec-
tor Protect register is cleared after reset and any previously written protection values will
be lost. User code must write this register in their initialization routine if they want to
enable sector protection.
When user code writes the Flash Sector Protect register, bits are set to 1 only. Thus, sectors
are protected, but not unprotected, using register write operations.
Flash Write Protection Option Bit
The Flash Write Protect option bit is enabled to block all program and erase operations
from user code. For detailed information, see
When the Flash Controller is unlocked, word writes to Program memory from user code
programs a word into the Flash if the address is located in the unlocked page. An erased
Flash word contains all ones (
from one to zero. To change a Flash bit (or multiple bits) from zero to one requires a Page
Erase or Mass Erase operation.
on page 289 and
On-Chip Debugger
P R E L I M I N A R Y
FFFFH
73H
). The programming operation is used to change bits
8CH
to the Flash Command register.
on page 295.
to the Flash Command register.
Option Bits
on page 289.
Product Specification
ZNEO
™
Flash Memory
Z16F Series
Option
256