2

Signal description

2.1

Serial clock (SCL)

The signal applied on the SCL input is used to strobe the data available on SDA(in) and to output the data on

SDA(out).

2.2

Serial data (SDA)

SDA is an input/output used to transfer data in or data out of the device. SDA(out) is an open drain output that

may be wire-OR'ed with other open drain or open collector signals on the bus. A pull-up resistor must be

connected from serial data (SDA) to VCC (Figure 11 indicates how to calculate the value of the pull-up resistor).

2.3

Write control (WC)

This input signal is useful for protecting the entire contents of the memory from inadvertent write operations. Write

operations are disabled to the entire memory array when write control (WC) is driven high. Write operations are

enabled when write control (WC) is either driven low or left floating.

When write control (WC) is driven high, device select and address bytes are acknowledged, Data bytes are not

acknowledged.

2.4

VSS (ground)

VSS is the reference for the VCC supply voltage.

2.5

Supply voltage (VCC)

2.5.1

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 Operating conditions in Section 8 DC and AC parameters). 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).

2.5.2

Power-up conditions

The VCC voltage has to rise continuously from 0 V up to the minimum VCC operating voltage (see Operating

conditions in Section 8 DC and AC parameters).

2.5.3

Device reset

In order to prevent inadvertent write operations during power-up, a power-on-reset (POR) circuit is included.

At power-up, the device does not respond to any instruction until VCC has reached the internal reset threshold

voltage. This threshold is lower than the minimum VCC operating voltage (see Operating conditions in

Section 8 DC and AC parameters). When VCC passes over the POR threshold, the device is reset and enters

the Standby Power mode; the device must not be accessed until VCC reaches a valid and stable DC voltage

within the specified [VCC(min), VCC(max)] range (see Operating conditions in Section 8 DC and AC parameters).

In a similar way, during power-down (continuous decrease in VCC), the device must not be accessed when VCC

drops below VCC(min). When VCC drops below the threshold voltage, the device stops responding to any

instruction sent to it.

2.5.4

Power-down conditions

During power-down (continuous decrease in VCC), the device must be in the standby power mode (mode reached

after decoding a Stop condition, assuming that there is no internal write cycle in progress).

M24C16-W M24C16-R M24C16-F

Signal description

DS9194 - Rev 11

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