M50FLW080A datasheet(35/64 Pages) STMICROELECTRONICS

35 / 64 page

M50FLW080A, M50FLW080B

Firmware Hub/low-pin-count (FWH/LPC) interface Configuration

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Firmware Hub/low-pin-count (FWH/LPC) interface

Configuration Registers

When the Firmware Hub Interface/Low Pin Count is selected, several additional registers

can be accessed. These registers control the protection status of the Blocks/Sectors, read

the General Purpose Input pins and identify the memory using the manufacturer code. See

Table 15 for the memory map of the Configuration Registers. The Configuration registers

are accessed directly without using any specific command code. A single Bus Write or Bus

Read Operation, with the appropriate address (including A22=0), is all that is needed.

6.1

Lock Registers

The Lock Registers control the protection status of the Blocks/Sectors. Each Block/Sector

has its own Lock Register. Three bits within each Lock Register control the protection of

each Block/Sector: the Write Lock Bit, the Read Lock Bit and the Lock Down Bit.

The Lock Registers can be read and written. Care should be taken, though, when writing.

Once the Lock Down Bit is set, ‘1’, further modifications to the Lock Register cannot be

made until it is cleared again by a reset or power-up.

See Table 16 for details on the bit definitions of the Lock Registers.

6.1.1

Write Lock

The Write Lock Bit determines whether the contents of the Block/Sector can be modified

(using the Program or Erase Command). When the Write Lock Bit is set, ‘1’, the

Block/Sector is write protected – any operations that attempt to change the data in the

Block/Sector will fail, and the Status Register will report the error. When the Write Lock Bit is

reset, ‘0’, the Block/Sector is not write protected by the Lock Register, and may be modified,

unless it is write protected by some other means.

If the Top Block Lock signal, TBL, is Low, VIL, then the Top Block (Block 15) is write

protected, and cannot be modified. Similarly, if the Write Protect signal, WP, is Low, VIL, then

the Main Blocks (Blocks 0 to 14) are write protected, and cannot be modified. For details,

see Appendix A and Table 16.

After power-up, or reset, the Write Lock Bit is always set to ‘1’ (write-protected).

6.1.2

Read Lock

The Read Lock bit determines whether the contents of the Block/Sector can be read (in

Read mode). When the Read Lock Bit is set, ‘1’, the Block/Sector is read protected – any

operation that attempts to read the contents of the Block/Sector will read 00h instead. When

the Read Lock Bit is reset, ‘0’, read operations are allowed in the Block/Sector, and return

the value of the data that had been programmed in the Block/Sector.

After power-up, or reset, the Read Lock Bit is always reset to ‘0’ (not read-protected).

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