ST72324Jx ST72324Kx
4 FLASH PROGRAM MEMORY
4.2 Main Features
■
■
■
■
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 individual sectors and programmed on a Byte-by-Byte basis using an external V
PP
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.
Three Flash programming modes:
– Insertion in a programming tool. In this mode, all sectors including option bytes can be programmed or erased.
– ICP (In-Circuit Programming). In this mode, all sectors including option bytes can be programmed or erased without removing the device from the application board.
– IAP (In-Application Programming) In this mode, all sectors except Sector 0, can be programmed or erased without removing the device 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
Register Access Security System (RASS) to prevent accidental programming or erasing
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 6 ). They are mapped in the upper part
of the ST7 addressing space so the reset and interrupt vectors are located in Sector 0 (F000h-
FFFFh).
Table 3. Sectors available in Flash devices
Flash Size (bytes)
4K
8K
> 8K
Available Sectors
Sector 0
Sectors 0,1
Sectors 0,1, 2
4.3.1 Read-out Protection
Read-out protection, when selected, provides a protection against Program Memory content extraction and against write access to Flash memory. Even if no protection can be considered as totally unbreakable, the feature provides a very high level of protection for a general purpose microcontroller.
In flash devices, this protection is removed by reprogramming the option. In this case, the entire program memory is first automatically erased.
Read-out protection selection depends on the device 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.
4.3 Structure
The Flash memory is organised in sectors and can be used for both code and data storage.
Figure 6. Memory Map and Sector Address
4K 8K 10K 16K
1000h
3FFFh
7FFFh
9FFFh
BFFFh
D7FFh
DFFFh
EFFFh
FFFFh
2 Kbytes
24K 32K 48K 60K
8 Kbytes 16 Kbytes
4 Kbytes
4 Kbytes
24 Kbytes 40 Kbytes 52 Kbytes
FLASH
MEMORY SIZE
SECTOR 2
SECTOR 1
SECTOR 0
17/164
1
