MC68HC908GR4MP datasheet(109/286 Pages) FREESCALE

109 / 286 page

MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7

Freescale Semiconductor

109

Chapter 11

Flash Memory

11.1 Introduction

This section describes the operation of the embedded FLASH memory. This memory can be read,

programmed, and erased from a single external supply. The program, erase, and read operations are

enabled through the use of an internal charge pump.

11.2 Functional Description

The FLASH memory is an array of 7,680 bytes for the MC68HC908GR8 or 4,096 bytes for the

MC68HC908GR4 with an additional 36 bytes of user vectors and one byte used for block protection. An

erased bit reads as 1 and a programmed bit reads as a 0. The program and erase operations are

facilitated through control bits in the Flash Control Register (FLCR). Details for these operations appear

later in this section.

The FLASH is organized internally as a 8192-word by 8-bit CMOS page erase, byte (8-bit) program

Embedded Flash Memory. Each page consists of 64 bytes. The page erase operation erases all words

within a page. A page is composed of two adjacent rows.

The address ranges for the user memory and vectors are as follows:

•

$E000–$FDFF; user memory for the MC68HC908GR8

$EE00–$FDFF; user memory for the MC68HC908GR4.

•

$FF7E; FLASH block protect register.

•$FE08; FLASH control register.

•

$FFDC–$FFFF; these locations are reserved for user-defined interrupt and reset vectors.

NOTE

A security feature prevents viewing of the FLASH contents.(1)

1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for

unauthorized users.

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