M950X0-W datasheet(10/46 Pages) STMICROELECTRONICS

10 / 46 page

Signal description

M950x0-W M950x0-R M950x0-DF

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DocID6512 Rev 13

2.8.3

Power-up conditions

When the power supply is turned on, VCC rises continuously 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 (see

Figure 3: Bus master and memory devices on the SPI bus).

In addition, the Chip Select (S) input offers a built-in safety feature, as the S input 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 voltage has to rise continuously from 0 V up to the minimum VCC operating voltage

defined in Table 9: Operating conditions (M950x0-W), Table 10: Operating conditions

(M950x0-R) and Table 11: Operating conditions (M95040-DF, device grade 6) and the rise

time must not vary faster than 1 V/µs.

2.8.4

Power-down

During power-down (continuous decrease in the VCC supply voltage below the minimum

VCC operating voltage defined in Table 9: Operating conditions (M950x0-W), Table 10:

Operating conditions (M950x0-R) and Table 11: Operating conditions (M95040-DF, device

grade 6)), the device must be:

•

Deselected (Chip Select S should be allowed to follow the voltage applied on VCC)

•

In Standby Power mode (there should not be any internal write cycle in progress).

M950X0-W Datasheet(PDF) 10 Page - STMicroelectronics