Z8F021ASH020SC datasheet(182/276 Pages) ZILOG

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PS022815-0206

Non-Volatile Data Storage

Z8 Encore! XP® 4K Series

Product Specification

163

Non-Volatile Data Storage

Overview

The Z8 Encore! XP® 4K Series devices contain a non-volatile data storage (NVDS) ele-

ment of up to 128 bytes. This memory can perform over 100,000 write cycles.

Operation

The NVDS is implemented by special purpose ZiLOG software stored in areas of program

memory not accessible to the user. These special-purpose routines use the Flash memory

to store the data. The routines incorporate a dynamic addressing scheme to maximize the

write/erase endurance of the Flash.

Different members of the Z8 Encore! XP® 4K Series feature multiple NVDS array sizes.

See Z8 Encore! XP® 4K Series Family Part Selection Guide on page 2 for details.

NVDS Code Interface

Two routines are required to access the NVDS: a write routine and a read routine. Both of

these routines are accessed with a CALL instruction to a pre-defined address outside of the

user-accessible program memory. Both the NVDS address and data are single-byte values.

Because these routines disturb the working register set, user code must ensure that any

required working register values are preserved by pushing them onto the stack or by

changing the working register pointer just prior to NVDS execution.

During both read and write accesses to the NVDS, interrupt service is NOT disabled. Any

interrupts that occur during the NVDS execution must take care not to disturb the working

interrupts before executing NVDS operations is recommended.

Use of the NVDS requires 15 bytes of available stack space. Also, the contents of the

working register set are overwritten.

For correct NVDS operation, the Flash Frequency Registers must be programmed based

on the system clock frequency (See Flash Operation Timing Using the Flash Frequency

Registers on page 140).

Note:

Z8F021ASH020SC 数据表(PDF) 182 Page - Zilog, Inc.