Version: **
Question:
RY/BY# output does not work as expected: it is stuck at BUSY state. Its state continuously changes after each reset. What is the reason?
Answer:
RY/BY# is an open-drain output pin that indicates whether an embedded flash operation is in progress. The advantage of open-drain output is that it provides flexibility in design; so, several open-drain outputs from different devices can be directly tied together in parallel to any voltage in the system, such as Vcc. All open-drain outputs require an external pull-up or pull-down resistor to keep the digital output in a defined logic state. For flash with RY/BY# LOW “0” for BUSY State, it always has to be held to HIGH “1” with a pull-up resistor (4.7K to 10K), to proceed to any operations. If RY/BY# is left unconnected without a pull-up resistor, RY/BY# is in floating state, undefined, and may not work as expected with its state wrongly interpreted as busy.
Table 1 shows Data Polling Status and RY/BY# state.
Table 1. RY/BY# State
