ST7LITEU09 datasheet(13/115 Pages) STMICROELECTRONICS

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ST7LITEU05 ST7LITEU09

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FLASH PROGRAM MEMORY (Cont’d)

5. A serial resistor must be connected to ICC con-

nector pin 6 in order to prevent contention on PA3/

RESET pin. Contention may occur if a tool forces a

state on RESET pin while PA3 pin forces the op-

posite state in output mode. The resistor value is

defined to limit the current below 2mA at 5V. If PA3

is used as output push-pull, then the application

must be switched off to allow the tool to take con-

trol of the RESET pin (PA3). To allow the program-

ming tool to drive the RESET pin below VIL, spe-

cial care must also be taken when a pull-up is

placed on PA3 for application reasons.

Caution: During normal operation, ICCCLK pin

must be pulled- up, internally or externally (exter-

nal pull-up of 10k mandatory in noisy environ-

ment). This is to avoid entering ICC mode unex-

pectedly during a reset. In the application, even if

the pin is configured as output, any reset will put it

back in input pull-up.

4.5 Memory Protection

There are two different types of memory protec-

tion: read-out protection and Write/Erase Protec-

tion which can be applied individually.

4.5.1 Read-out Protection

Readout protection, when selected provides a pro-

tection against program memory content extrac-

tion 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.

Program memory is protected.

In flash devices, this protection is removed by re-

programming the option. In this case, program

memory is 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.

4.5.2 Flash Write/Erase Protection

Write/erase protection, when set, makes it impos-

sible to both overwrite and erase program memo-

ry. Its purpose is to provide advanced security to

applications and prevent any change being made

to the memory content.

Warning: Once set, Write/erase protection can

never be removed. A write-protected flash device

is no longer reprogrammable.

Write/erase protection is enabled through the

FMP_W bit in the option byte.

4.6 Related Documentation

For details on Flash programming and ICC proto-

col, refer to the ST7 Flash Programming Refer-

ence Manual and to the ST7 ICC Protocol Refer-

ence Manual

4.7 Register Description

FLASH CONTROL/STATUS REGISTER (FCSR)

Read/Write

Reset Value: 000 0000 (00h)

1st RASS Key: 0101 0110 (56h)

2nd RASS Key: 1010 1110 (AEh)

Note: This register is reserved for programming

using ICP, IAP or other programming methods. It

controls the XFlash programming and erasing op-

erations.

When an EPB or another programming tool is

used (in socket or ICP mode), the RASS keys are

sent automatically.

Table 4. FLASH Register Map and Reset Values

000

OPT

LAT

PGM

Address

(Hex.)

Label

76543

210

002Fh

FCSR

Reset Value

00000

OPT

LAT

PGM

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