Z8F640x/Z8F480x/Z8F320x/Z8F240x/Z8F160x
Z8 Encore!®
148
Option Bits
Overview
Option Bits allow user configuration of certain aspects of Z8F640x family device opera-
tion. The feature configuration data is stored in the Program Memory and read during
Reset. The features available for control via the Option Bits are:
•
•
•
•
Watch-Dog Timer time-out response selection–interrupt or Short Reset.
Watch-Dog Timer enabled at Reset.
The ability to prevent unwanted read access to user code in Program Memory.
The ability to prevent accidental programming and erasure of all or a portion of the
user code in Program Memory.
Operation
Option Bit Configuration By Reset
Each time the Option Bits are programmed or erased, the Z8F640x family device must be
Reset for the change to take place. During any reset operation (System Reset, Short Reset,
or Stop Mode Recovery), the Option Bits are automatically read from the Program Mem-
ory and written to Option Configuration registers. The Option Configuration registers con-
trol operation of the Z8F640x family device. Option Bit control of the Z8F640x family
device is established before the device exits Reset and the eZ8 CPU begins code execu-
tion. The Option Configuration registers are not part of the Register File and are not acces-
sible for read or write access.
Option Bit Address Space
The first two bytes of Program Memory at addresses 0000Hand 0001Hare reserved for
the user Option Bits. The byte at Program Memory address 0000His used to configure
user options. The byte at Program Memory address 0001His reserved for future use and
must be left in its unprogrammed state.
PS017610-0404
Option Bits
ZILOG [ ZILOG, INC. ]
