M95128-RMB6TPSLASHA datasheet(10/44 Pages) STMICROELECTRONICS

10 / 44 page

Signal description

M95128, M95128-W, M95128-R

10/44

3.6

Write Protect (W)

The main purpose of this input signal is to freeze the size of the area of memory that is

protected against Write instructions (as specified by the values in the BP1 and BP0 bits of

the Status Register).

This pin must be driven either High or Low, and must be stable during all write instructions.

3.7

Supply voltage (VCC)

3.7.1

Operating supply voltage VCC

Prior to selecting the memory and issuing instructions to it, a valid and stable VCC voltage

within the specified [VCC(min), VCC(max)] range must be applied (see Table 7, Table 8 and

Table 9). In order to secure a stable DC supply voltage, it is recommended to decouple the

VCC line with a suitable capacitor (usually of the order of 10 nF to 100 nF) close to the

VCC/VSS package pins.

This voltage must remain stable and valid until the end of the transmission of the instruction

and, for a Write instruction, until the completion of the internal write cycle (tW).

3.7.2

Power-up conditions

When the power supply is turned on, VCC continuously rises from VSS to VCC. During this

time, the Chip Select (S) line is not allowed to float but should follow the VCC voltage, it is

therefore recommended to connect the S line to VCC via a suitable pull-up resistor.

In addition, the Chip Select (S) input offers a built-in safety feature, as it is edge-sensitive as

well as level-sensitive: after power-up, the device does not become selected until a falling

edge has first been detected on Chip Select (S). This ensures that Chip Select (S) must

have been high, prior to going low to start the first operation.

The VCC rise time must not vary faster than 1 V/µs.

3.7.3

Device reset

In order to prevent inadvertent Write operations during power-up (continuous rise of VCC), a

power on reset (POR) circuit is included. At power-up, the device does not respond to any

instruction until the VCC has reached the power on reset threshold voltage (this threshold is

lower than the minimum VCC operating voltage defined in Table 7, Table 8 and Table 9).

When VCC passes over the POR threshold, the device is reset and is in the following state:

●

Standby Power mode

●

deselected (at next power-up, a falling edge is required on Chip Select (S) before any

instruction can be started).

●

not in the Hold Condition

●

Status register:

–

the Write Enable Latch (WEL) is reset to 0

–

the Write In Progress (WIP) is reset to 0

–

The SRWD, BP1 and BP0 bits of the Status Register are unchanged from the

previous power-down (they are non-volatile bits)

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