ZUSBOPTSC01ZACG datasheet(166/282 Pages) ZILOG

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PS022827-1212

P R E L I M I N A R Y

Operation

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 32kHz (32768Hz) through 20MHz.

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:

Flash programming and erasure are not supported for system clock frequencies below

32kHz (32768Hz) or above 20MHz. 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.

FFREQ[15:0]

System Clock Frequency (Hz)

1000

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