4.1.1.1 Resetting the Device

A Reset and Discovery Response sequence is used by the host to reset the device as well as to perform a general bus call to determine if any devices are present on the bus.

To begin the Reset portion of the sequence, the host must drive SI/O low for a minimum time. If the device is not currently busy with other operations, the host can drive SI/O low for a time of t_RESET. The length of t_RESET differs for Standard Speed mode and for High-Speed mode.

However, if the device is busy, the host must drive SI/O for a time of t_DSCHG to ensure the device is reset as discussed in Interrupting the Device during an Active Operation. The Reset time forces any internal charge storage within the device to be consumed, causing the device to lose all remaining standby power available internally.

Upon SI/O being released for a sufficient amount of time to allow the device time to power-up and initialize, the host must then always request a Discovery Response Acknowledge from the AT21CS01/AT21CS11 prior to any commands being sent to the device. The host can then determine if an AT21CS01/AT21CS11 is present by sampling for the Discovery Response Acknowledge from the device.