4.5.1.1 Device Reset

To prevent inadvertent write operations or any other spurious events from occurring during a power-up sequence, the AT24C256C includes a Power-on Reset (POR) circuit. Upon power-up, the device will not respond to any commands until the V_CC level crosses the internal voltage threshold (V_POR) that brings the device out of Reset and into Standby mode.

The system designer must ensure the instructions are not sent to the device until the V_CC supply has reached a stable value greater than or equal to the minimum V_CC level. Additionally, once the V_CC is greater than or equal to the minimum V_CC level, the bus host must wait at least t_PUP before sending the first command to the device. See Table 4-4 for the values associated with these power-up parameters.

Table 4-4. Power-Up Conditions⁽¹⁾
Symbol	Parameter	Min.	Max.	Units
t_PUP	Time required after V_CC is stable before the device can accept commands	100	－	µs
V_POR	Power-on Reset Threshold Voltage	－	1.5	V
t_POFF	Minimum time at V_CC = 0V between power cycles	500	－	ms

Note:

These parameters are characterized but they are not 100% tested in production.

If an event occurs in the system where the V_CC level supplied to the AT24C256C drops below the maximum V_POR level specified, it is recommended that a full-power cycle sequence be performed by first driving the V_CC pin to GND, waiting at least the minimum t_POFF time and then performing a new power-up sequence in compliance with the requirements defined in this section.