Author: TakahiroK_16 Version: **
Translation - Japanese: https://community.cypress.com/docs/DOC-20313
What is the recommended configuration for the RWDS pin in HyperBus memory?
Weak pull-down is recommended for the RWDS pin in HyperBus memory.
The RWDS is used as a source for synchronous read Data Strobe (DS), an input signal (clock) for the host controller. In general, you should not leave input signals floating to prevent unknown or intermediate state of input signals. For the RWDS pin, weak pull-down is recommended. The memory stops driving the RWDS pin at logical low state at the end of the operation (Figure 1). Weak pull-down can keep the RWDS pin at logical low state until the next operation begins. Figure 2 and Figure 3 compare the weak pull-down and weak pull-up in back-to-back read operation case.
Figure 1. HyperBus Read Operation
Figure 2. Back-to-Back Read Operations – Weak Pull-Down for RWDS
Figure 3. Back-to-Back Read Operations – Weak Pull-Up for RWDS