PSD4235G2V_09 datasheet(45/124 Pages) STMICROELECTRONICS

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PSD4235G2V

Specific features

45/124

Specific features

10.1

Flash Memory Sector Protect

Each sector of primary or secondary Flash memory can be separately protected against

Program and Erase cycles. Sector Protection provides additional data security because it

disables all Program or Erase cycles. This mode can be activated (or deactivated) through

the JTAG-ISP Port or a device programmer.

Sector protection can be selected for each sector using the PSDsoft Express program. This

automatically protects selected sectors when the device is programmed through the JTAG

Port or a device programmer. Flash memory sectors can be unprotected to allow updating of

their contents using the JTAG Port or a device programmer. The MCU can read (but cannot

change) the sector protection bits.

Any attempt to program or erase a protected Flash memory sector is ignored by the device.

The Verify operation results in a READ of the protected data. This allows a guarantee of the

retention of the Protection status.

The sector protection status can be read by the MCU through the Flash memory protection

and secondary Flash memory protection registers (in the CSIOP block) or use the Read

Sector Protection instruction. See Table 18 to Table 19.

10.2

Reset

The Reset instruction consists of one WRITE cycle (see Table 28). It can also be optionally

preceded by the standard two WRITE decoding cycles (writing AAh to AAAh, and 55h to

554h).

The Reset instruction must be executed after:

●

Reading the Flash Protection Status or Flash ID

●

An Error condition has occurred (and the device has set the Error Flag bit (DQ5/DQ13)

to ’1’) during a Flash memory Program or Erase cycle.

The Reset instruction immediately puts the Flash memory back into normal READ mode.

However, if there is an error condition (with the Error Flag bit (DQ5/DQ13) set to ’1’) the

Flash memory will return to the READ mode in 25

μs after the Reset instruction is issued.

The Reset instruction is ignored when it is issued during a Program or Bulk Erase cycle of

the Flash memory. The Reset instruction aborts any on-going Sector Erase cycle, and

returns the Flash memory to the normal READ mode in 25

μs.

10.3

Reset (RESET) pin

A pulse on the Reset (RESET) pin aborts any cycle that is in progress, and resets the Flash

memory to the READ mode. When the reset occurs during a Program or Erase cycle, the

Flash memory takes up to 25

μs to return to the READ mode. It is recommended that the

Reset (RESET) pulse (except for Power-on Reset, as described in Section 21.1) be at least

μs so that the Flash memory is always ready for the MCU to fetch the bootstrap

instructions after the Reset cycle is complete.

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