Datasheet

FLASH Memory (FLASH)

MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 4

Freescale Semiconductor 39

The address ranges for the user memory and vectors are:

• $C000–$FDFF; user memory

•$FE08

; FLASH control register

• $FF7E; FLASH block protect register

• $FFD4–$FFFF; these locations are reserved for user-defined interrupt and reset vectors

Programming tools are available from Freescale Semiconductor. Contact your local representative for

more information.

NOTE

A security feature prevents viewing of the FLASH contents.

(1)

2.6.2 FLASH Control Register

The FLASH control register (FLCR) controls FLASH program and erase operations.

HVEN — High-Voltage Enable Bit

This read/write bit enables the charge pump to drive high voltages for program and erase operations

in the array. HVEN can only be set if either PGM = 1 or ERASE = 1 and the proper sequence for

program or erase is followed.

1 = High voltage enabled to array and charge pump on

0 = High voltage disabled to array and charge pump off

MASS — Mass Erase Control Bit

Setting this read/write bit configures the 16-Kbyte FLASH array for mass erase operation.

1 = MASS erase operation selected

0 = PAGE erase operation selected

ERASE — Erase Control Bit

This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit

such that both bits cannot be equal to 1 or set to 1 at the same time.

1 = Erase operation selected

0 = Erase operation unselected

PGM — Program Control Bit

This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE

bit such that both bits cannot be equal to 1 or set to 1 at the same time.

1 = Program operation selected

0 = Program operation unselected

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

unauthorized users.

Address: $FE08

Bit 7654321Bit 0

HVEN MASS ERASE PGM

Write:

Reset:00000000

= Unimplemented

Figure 2-3. FLASH Control Register (FLCR)