ST72F321 datasheet(17/189 Pages) STMICROELECTRONICS

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ST72321

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4 FLASH PROGRAM MEMORY

4.1 Introduction

The ST7 dual voltage High Density Flash

(HDFlash) is a non-volatile memory that can be

electrically erased as a single block or by individu-

al sectors and programmed on a Byte-by-Byte ba-

sis using an external VPP supply.

The HDFlash devices can be programmed and

erased off-board (plugged in a programming tool)

or on-board using ICP (In-Circuit Programming) or

IAP (In-Application Programming).

The array matrix organisation allows each sector

to be erased and reprogrammed without affecting

other sectors.

4.2 Main Features

■ Three Flash programming modes:

– Insertion in a programming tool. In this mode,

all sectors including option bytes can be pro-

grammed or erased.

– ICP (In-Circuit Programming). In this mode, all

sectors including option bytes can be pro-

grammed or erased without removing the de-

vice from the application board.

– IAP (In-Application Programming) In this

mode, all sectors except Sector 0, can be pro-

grammed or erased without removing the de-

vice from the application board and while the

application is running.

■ ICT (In-Circuit Testing) for downloading and

executing user application test patterns in RAM

■ Read-out protection against piracy

■ Register Access Security System (RASS) to

prevent accidental programming or erasing

4.3 Structure

The Flash memory is organised in sectors and can

be used for both code and data storage.

Depending on the overall Flash memory size in the

microcontroller device, there are up to three user

sectors (see Table 3). Each of these sectors can

be erased independently to avoid unnecessary

erasing of the whole Flash memory when only a

partial erasing is required.

The first two sectors have a fixed size of 4 Kbytes

(see Figure 5). They are mapped in the upper part

of the ST7 addressing space so the reset and in-

terrupt vectors are located in Sector 0 (F000h-

FFFFh).

Table 3. Sectors available in Flash devices

4.3.1 Read-out Protection

Read-out protection, when selected, provides a

protection against Program Memory content ex-

traction and against write access to Flash memo-

ry. Even if no protection can be considered as to-

tally unbreakable, the feature provides a very high

level of protection for a general purpose microcon-

troller.

In flash devices, this protection is removed by re-

programming the option. In this case, the entire

program memory is first automatically erased and

the device can be reprogrammed.

Read-out protection selection depends on the de-

vice type:

– In Flash devices it is enabled and removed

through the FMP_R bit in the option byte.

– In ROM devices it is enabled by mask option

specified in the Option List.

Note: In flash devices, the LVD is not supported if

read-out protection is enabled.

Figure 5. Memory Map and Sector Address

Flash Size (bytes)

Available Sectors

Sector 0

Sectors 0,1

> 8K

Sectors 0,1, 2

4 Kbytes

2Kbytes

SECTOR 1

SECTOR 0

16 Kbytes

SECTOR 2

16K

32K

60K

FLASH

FFFFh

EFFFh

DFFFh

3FFFh

7FFFh

1000h

24 Kbytes

MEMORY SIZE

8Kbytes

40 Kbytes 52 Kbytes

9FFFh

BFFFh

D7FFh

10K

24K

48K

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