PSD813F1 datasheet(30/110 Pages) STMICROELECTRONICS

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PSD813F1

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FLASH AND EEPROM MEMORY SPECIFIC FEATURES

Flash Memory and EEPROM Sector Protect

Each Flash and EEPROM sector can be separate-

ly protected against Program and Erase functions.

Sector Protection provides additional data security

because it disables all program or erase opera-

tions. This mode can be activated through the

JTAG Port or a Device Programmer.

Sector protection can be selected for each sector

using the PSDsoft Configuration program. This will

automatically protect selected sectors when the

device is programmed through the JTAG Port or a

Device Programmer. Flash and EEPROM sectors

can be unprotected to allow updating of their con-

tents using the JTAG Port or a Device Program-

mer. The microcontroller can read (but cannot

change) the sector protection bits.

Any attempt to program or erase a protected Flash

or EEPROM sector will be ignored by the device.

The Verify operation will result in a READ of the

protected data. This allows a guarantee of the re-

tention of the Protection status.

The sector protection status can be read by the

MCU through the Flash protection and PSD/EE

protection registers (CSIOP). See Table 10.

Reset

The Reset instruction resets the internal memory

logic state machine in a few milliseconds. Reset is

an instruction of either one write operation or three

write operations (refer to Table 8., page 20).

Table 10. Sector Protection/Security Bit Definition – Flash Protection Register

Note: 1. Bit Definitions:

Sec_Prot 1 = Flash is write protected.

Sec_Prot 0 = Flash is not write protected.

Table 11. Sector Protection/Security Bit Definition – PSD/EE Protection Register

Note: 1. Bit Definitions:

Sec_Prot 1 = EEPROM Boot Sector is write protected.

Sec_Prot 0 = EEPROM Boot Sector is not write protected.

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

1 = Security Bit in device has been set.

SRAM

The SRAM is a 16 Kbit (2K x 8) memory. The

SRAM is enabled when RS0—the SRAM chip se-

lect output from the DPLD—is high. RS0 can con-

tain up to two product terms, allowing flexible

memory mapping.

The SRAM can be backed up using an external

battery. The external battery should be connected

to the VSTBY pin (PC2). If you have an external

battery connected to the PSD, the contents of the

SRAM will be retained in the event of a power loss.

The contents of the SRAM will be retained so long

as the battery voltage remains at 2V or greater.

If the supply voltage falls below the battery volt-

age, an internal power switchover to the battery

occurs.

Pin PC4 can be configured as an output that indi-

cates when power is being drawn from the exter-

nal battery. This VBATON signal will be high with

the supply voltage falls below the battery voltage

and the battery on PC2 is supplying power to the

internal SRAM.

The chip select signal (RS0) for the SRAM, VSTBY,

and VBATON are all configured using PSDsoft Ex-

press Configuration.

Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1

Bit 0

Sec7_Prot

Sec6_Prot

Sec5_Prot

Sec4_Prot

Sec3_Prot

Sec2_Prot

Sec1_Prot

Sec0_Prot

Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1

Bit 0

Security_Bit

not used

Sec3_Prot

Sec2_Prot

Sec1_Prot

Sec0_Prot

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