Z8F6421PM020SC Datasheet, PDF (210/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
190
Option Bits
Overview
Option Bits allow user configuration of certain aspects of the 64K Series operation. The
feature configuration data is stored in the Flash Memory and read during Reset. The fea-
tures available for control via the Option Bits are:
• Watch-Dog Timer time-out response selection–interrupt or Reset.
• Watch-Dog Timer enabled at Reset.
• The ability to prevent unwanted read access to user code in Flash Memory.
• The ability to prevent accidental programming and erasure of the user code in Flash
Memory.
• Voltage Brown-Out configuration-always enabled or disabled during STOP mode to
reduce STOP mode power consumption.
• Oscillator mode selection-for high, medium, and low power crystal oscillators, or
external RC oscillator.
Operation
Option Bit Configuration By Reset
Each time the Option Bits are programmed or erased, the device must be Reset for the
change to take place. During any reset operation (System Reset, Reset, or STOP Mode
Recovery), the Option Bits are automatically read from the Flash Memory and written to
Option Configuration registers. The Option Configuration registers control operation of
the devices within the 64K Series. Option Bit control is established before the device exits
Reset and the eZ8 CPU begins code execution. The Option Configuration registers are not
part of the Register File and are not accessible for read or write access.
Option Bit Address Space
The first two bytes of Flash Memory at addresses 0000H (Table 97) and 0001H (Table 98)
are reserved for the user Option Bits. The byte at Flash Memory address 0000H configures
user options. The byte at Flash Memory address 0001H is reserved for future use and must
remain unprogrammed.
PS019915-1005
Option Bits