Z8F1680SH020SG Datasheet, PDF (292/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
267
20.2.1. Flash Operation Timing Using Flash Frequency
Registers
Before performing either a program or erase operation on Flash memory, you must first
configure the Flash frequency High and Low Byte registers. The Flash frequency registers
allow programming and erasing of the Flash with system clock frequencies ranging from
32 kHz (32768 Hz) through 20 MHz.
The Flash frequency High and Low Byte registers combine to form a 16-bit value,
FFREQ, to control timing for flash program and erase operations. The 16-bit binary Flash
frequency value must contain the system clock frequency (in kHz). This value is calcu-
lated using the following equation:
FFREQ[15:0] = ^{S-----y---s--t--e----m------C-----l-o---c---k-----F----r--e---q---u----e---n---c---y-----(--H----z---)-}
1000
Caution: Flash programming and erasure are not supported for system clock frequencies below
32 kHz (32768 Hz) or above 20 MHz. The Flash Frequency High and Low Byte registers
must be loaded with the correct value to ensure operation of the Z8 Encore! XP F1680
Series devices.
20.2.2. Flash Code Protection Against External Access
The user code contained within Flash memory can be protected against external access
with the On-Chip Debugger. Programming the FRP Flash option bit prevents reading of
the user code with the On-Chip Debugger. For more details, see the Flash Option Bits
chapter on page 276 and the On-Chip Debugger chapter on page 294.
20.2.3. Flash Code Protection Against Accidental Program
and Erasure
The Z8 Encore! XP F1680 Series provides several levels of protection against accidental
program and erasure of the contents of Flash memory. This protection is provided by a
combination of the Flash Option bits, the register locking mechanism, the page select
redundancy and the sector level protection control of the Flash Controller.
20.2.3.1. Flash Code Protection Using the Flash Option Bits
The FWP Flash option bit provides Flash Program Memory protection as listed in Table
133. For more details, see the Flash Option Bits chapter on page 276.
PS025015-1212
PRELIMINARY
Flash Memory