M95010 datasheet(9/42 Pages) STMICROELECTRONICS

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M95040, M95020, M95010

Signal description

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2.6

Write Protect (W)

This input signal is used to control whether the memory is write protected. When Write

Protect (W) is held Low, writes to the memory are disabled, but other operations remain

enabled. Write Protect (W) must either be driven High or Low, but must not be left floating.

2.7

VSS ground

VSS is the reference for the VCC supply voltage.

2.8

Supply voltage (VCC)

VCC is the supply voltage.

2.8.1

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 8, Table 9 and

Table 10). 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 10nF to 100nF) 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).

2.8.2

Power-up conditions

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

Select (S) signal is not allowed to float and must follow the VCC voltage. The S line should

therefore be connected to VCC via a suitable pull-up resistor.

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

sensitive and level sensitive. Practically this means that after power-up, the device cannot

become selected until a falling edge has first been detected on Chip Select (S). So the Chip

Select (S) signal must first have been High, and then gone Low before the first operation can

be started.

2.8.3

Internal device reset

In order to prevent inadvertent Write operations during Power-up, a Power On Reset (POR)

circuit is included. At Power-up (continuous rise of VCC), the device will not respond to any

instruction until VCC has reached the Power On Reset threshold voltage (this threshold is

lower than the minimum VCC operating voltage defined in Section 9: DC and AC

parameters).

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