Z8F042ASJ020EG2156 Datasheet, PDF (164/280 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F082A Series
Product Specification
149
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
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 F082A
Series devices.
Flash Code Protection Against External Access
The user code contained within the Flash memory can be protected against external access
by the on-chip debugger. Programming the FRP Flash option bit prevents reading of the
user code with the On-Chip Debugger. See the Flash Option Bits chapter on page 159 and
the On-Chip Debugger chapter on page 180 for more information.
Flash Code Protection Against Accidental Program and
Erasure
The Z8 Encore! XP F082A Series provides several levels of protection against accidental
program and erasure of the Flash memory contents. This protection is provided by a com-
bination of the Flash option bits, the register locking mechanism, the page select redun-
dancy 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 shown in Table 79. See the Flash Option Bits chapter on page 159
for more information.
PS022828-0413
PRELIMINARY
Operation