Z8F0113HJ005EG Datasheet, PDF (152/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
137
Flash Operation Timing Using the 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 regis-
ters 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 Fre-
quency value must contain the system clock frequency (in kHz). This value is calculated
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 Z8 Encore! XP F0823 Series
devices.
Flash Code Protection Against External Access
The user code contained within the 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 information, see the Flash Option Bits
section on page 146 and the On-Chip Debugger chapter on page 156.
Flash Code Protection Against Accidental Program and
Erasure
F0823 Series provides several levels of protection against accidental program and erasure
of the Flash memory contents. 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.
Flash Code Protection Using the Flash Option Bits
The FRP and FWP Flash Option Bits combine to provide three levels of Flash Program
Memory protection as listed in Table 80. For more information, see the Flash Option Bits
section on page 146.
PS024315-1011
PRELIMINARY
Operation