Wiznet W7500 Reference Manual page 410

enables write access to all other registers. Writing any other value disables write
accesses. A read from this register returns only the bottom bit.
[0] WES – Register Write Enable status.
0 : Indicates that write access is enabled, not locked. Default.
1 : Indicates that write access is disabled, locked.
[31:1] ERW – Enable Register Writes
Enable write access to all other registers by writing 0x1ACCE551. Disable
write access by writing any other value.
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