Z8F0113HJ005EG Datasheet, PDF (154/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
139
bits can only be set to 1. Thus, sectors can be protected, but not unprotected, via register
write operations. Writing a value other than 5EH to the Flash Control Register deselects
the Flash Sector Protect Register and reenables access to the Page Select Register.
Observe the following procedure to setup the Flash Sector Protect Register from user
code:
1. Write 00H to the Flash Control Register to reset the Flash Controller.
2. Write 5EH to the Flash Control Register to select the Flash Sector Protect Register.
3. Read and/or write the Flash Sector Protect Register which is now at Register File
address FF9H.
4. Write 00H to the Flash Control Register to return the Flash Controller to its reset state.
The Sector Protect Register is initialized to 0 on reset, putting each sector into an unpro-
tected state. When a bit in the Sector Protect Register is written to 1, the corresponding
sector can no longer be written or erased by the CPU. External Flash programming
through the OCD or via the Flash Controller Bypass mode are unaffected. After a bit of
the Sector Protect Register has been set, it cannot be cleared except by powering down the
device.
Byte Programming
The Flash Memory is enabled for byte programming after unlocking the Flash Controller
and successfully enabling either Mass Erase or Page Erase. When the Flash Controller is
unlocked and Mass Erase is successfully completed, all Program Memory locations are
available for byte programming. In contrast, when the Flash Controller is unlocked and
Page Erase is successfully enabled, only the locations of the selected page are available for
byte programming. An erased Flash byte contains all 1’s (FFH). The programming opera-
tion can only be used to change bits from 1 to 0. To change a Flash bit (or multiple bits)
from 0 to 1 requires execution of either the Page Erase or Mass Erase commands.
Byte Programming is accomplished using the On-Chip Debugger's Write Memory com-
mand or eZ8 CPU execution of the LDC or LDCI instructions. For a description of the
LDC and LDCI instructions, refer to the eZ8 CPU Core User Manual (UM0128), available
for download at www.zilog.com. While the Flash Controller programs the Flash memory,
the eZ8 CPU idles but the system clock and on-chip peripherals continue to operate. To
exit programming mode and lock the Flash, write any value to the Flash Control Register,
except the Mass Erase or Page Erase commands.
Caution: The byte at each address of the Flash memory cannot be programmed (any bits written
to 0) more than twice before an erase cycle occurs. Doing so may result in corrupted data
at the target byte.
PS024315-1011
PRELIMINARY
Operation