Read Operation in Software Write Protect in Parallel F-RAM - KBA229133

Version 6

    Version: **

     

    Usually, a complete read operation includes two steps:

    1. CE asserts LOW while /WE keeps HIGH.
    2. OE asserts LOW to drive the data bus.

    When accessing write protect mode, the system host must issue read commands in a special sequence. In this case, the value of OE is “don’t care”, because the device will recognize it as a read operation when CE is LOW and /WE is HIGH. As shown in Figure 1 and Figure 2 which are from the datasheets, OE  keeps HIGH in the sequences to set write-protect blocks and read write-protect settings. Only in reading the write-protect setting data, OE asserts LOW.

    Note: This is applicable for FM22L16, FM22LD16, CY15B102N, and FM28V202A family devices.

     

    Figure 1. Write-Protect Sequence for CY15B102N, FM28V202A

    1. Sequence to Set Write-Protect Blocks

     

    2. Sequence to Read Write-Protect Settings

     

    Figure 2. Write-Protect Sequence for FM22L16, FM22LD16

    1. Sequence to Set Write-Protect Blocks

    2. Sequence to Read Write-Protect Settings