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PSD853F5V90UI

Flash In-System Programmable (ISP) Peripherals for 8-bit MCUs, 5V

STMicroelectronics 

PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2

SPECIFIC FEATURES

Flash Memory Sector Protect

Each primary and secondary Flash memory sector

can be separately protected against Program and

Erase cycles. Sector Protection provides addition-

al data security because it disables all Program or

Erase cycles. This mode can be activated through

the JTAG Port or a Device Programmer.

Sector protection can be selected for each sector

using the PSDsoft Express Configuration pro-

gram. This automatically protects selected sectors

when the device is programmed through the JTAG

Port or a Device Programmer. Flash memory sec-

tors can be unprotected to allow updating of their

contents using the JTAG Port or a Device Pro-

grammer. 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 Pro-

tection status.

The sector protection status can be read by the

MCU through the Flash memory protection and

PSD/EE protection registers (in the CSIOP block).

See Tables 11 and 12.

Reset Flash

The Reset Flash instruction consists of one

WRITE cycle (see Table 9., page 21). It can also

be optionally preceded by the standard two

WRITE decoding cycles (writing AAh to 555h and

55h to AAAh). It 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) to '1')

during a Flash memory Program or Erase

cycle.

On the PSD813F2/3/4/5, the Reset Flash instruc-

tion puts the Flash memory back into normal

READ Mode. It may take the Flash memory up to

a few milliseconds to complete the Reset cycle.

The Reset Flash instruction is ignored when it is is-

sued during a Program or Bulk Erase cycle of the

Flash memory. The Reset Flash instruction aborts

any on-going Sector Erase cycle, and returns the

Flash memory to the normal READ Mode within a

few milliseconds.

On the PSD83xF2 or PSD85xF2, the Reset Flash

instruction puts the Flash memory back into nor-

mal READ Mode. If an Error condition has oc-

curred (and the device has set the Error Flag Bit

(DQ5) to '1') the Flash memory is put back into nor-

mal READ Mode within 25µs of the Reset Flash in-

struction having been issued. The Reset Flash

instruction is ignored when it is issued during a

Program or Bulk Erase cycle of the Flash memory.

The Reset Flash instruction aborts any on-going

Sector Erase cycle, and returns the Flash memory

to the normal READ Mode within 25µs.

Reset (RESET) Signal (on the PSD83xF2 and

PSD85xF2)

A pulse on Reset (RESET) aborts any cycle that is

in progress, and resets the Flash memory to the

READ Mode. When the reset occurs during a Pro-

gram or Erase cycle, the Flash memory takes up

to 25µs to return to the READ Mode. It is recom-

mended that the Reset (RESET) pulse (except for

Power On Reset, as described on RESET TIMING

AND DEVICE STATUS AT RESET, page 67) be

at least 25µs so that the Flash memory is always

ready for the MCU to fetch the bootstrap instruc-

tions after the Reset cycle is complete.

Table 11. Sector Protection/Security Bit Definition – Flash Protection Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Sec7_Prot Sec6_Prot Sec5_Prot Sec4_Prot Sec3_Prot Sec2_Prot Sec1_Prot

Note: 1. Bit Definitions:

Sec<i>_Prot 1 = Primary Flash memory or secondary Flash memory Sector <i> is write protected.

Sec<i>_Prot 0 = Primary Flash memory or secondary Flash memory Sector <i> is not write protected.

Bit 0

Sec0_Prot

Table 12. Sector Protection/Security Bit Definition – PSD/EE Protection Register

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Security_Bit not used

not used

not used

Sec3_Prot Sec2_Prot Sec1_Prot

Note: 1. Bit Definitions:

Sec<i>_Prot 1 = Secondary Flash memory Sector <i> is write protected.

Sec<i>_Prot 0 = Secondary Flash memory Sector <i> is not write protected.

Security_Bit 0 = Security Bit in device has not been set.

1 = Security Bit in device has been set.

Bit 0

Sec0_Prot

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