1. Define the protected write scope
A write-protection requirement must identify the storage scope being protected. The phrase write protected can otherwise leave it unclear whether the design expects one region, the whole array or another mechanism. Microchip's 24XX256 description is explicit about the entire-array scope of its hardware WP function. Use that stated scope rather than assigning a narrower region simply because the application wants to preserve only some data.
This is a coverage question, distinct from memory capacity or the address representation used to reach data. A device may have the expected storage identity while its protection mechanism has a different scope from the requested one. Keeping coverage as its own requirement exposes that difference before a candidate is described as suitable on the basis of a general EEPROM label.
A requirement for selective protection therefore needs its own applicable evidence. The named full-array example does not supply it, even if the intended use concerns a small portion of the memory. Preserve what the documented mechanism actually inhibits. This avoids treating an application wish as a product capability or confusing an addressing question with a write-protection boundary.
2. Read the hardware WP meaning
Microchip describes WP as a hardware input whose stated condition enables or inhibits writes for the named family. The useful sourcing distinction is the documented effect of that input, not an assumed physical connection on a particular board. An exact component can offer the function while the implementation still requires evidence of how the application uses it.
Keep the protection mechanism separate from a software convention not to write. The manufacturer statement concerns a hardware-controlled inhibition of write operations. A program that avoids issuing a write command describes another layer of behaviour. Recording which mechanism the design requires makes the comparison more precise without reconstructing firmware or prescribing how to connect the device.
The physical pin assignment and the application's connection record belong to exact-device implementation evidence. A general WP description cannot identify those details for an unknown assembly. This guide therefore uses the input's documented functional meaning without providing a pin map or a wiring sequence. The required protection effect and the actual implementation should remain separately assessable.
3. Keep reads separate from inhibited writes
Read access remains a different operation. Section 2.4 states that the named write-protection condition does not affect reads. This matters when interpreting protected storage: inhibiting changes to the array does not necessarily prevent the system from retrieving the data already present. A requirement to block reading would therefore need a different supporting statement rather than a broader interpretation of WP.
The write descriptions also distinguish command acknowledgement from an actual write cycle. Microchip explains that the device can acknowledge an attempted write command while protection prevents a write cycle and no data is written. An acknowledgement is therefore not, by itself, evidence that the protected contents changed. Preserve the operation-specific meaning when discussing the named behaviour.
These distinctions prevent a single access-permitted label from obscuring what happened. Reading, accepting a command and changing stored data are not interchangeable descriptions. The requirement should identify the operation that must be allowed or inhibited. This is not a security classification or an erasure capability; those would need evidence beyond the documented write-protect function used here.
4. Preserve write-cycle timing boundaries
The write-command timing boundary is part of the protection meaning. Microchip's section 6.3 states that WP is sampled at the STOP bit for each write command. The same section says a later change to WP does not affect execution of that write cycle. Retain both statements rather than describing the input as an unrestricted intervention at any instant.
This creates a distinction between preventing the relevant write cycle and trying to alter one after its documented sampling point. A requirement that depends on immediate cancellation cannot be established from the earlier protection description alone. The exact timing rule matters even when the coverage requirement is already understood, because entire-array protection says where the mechanism applies, not when a changed state takes effect.
Keep this timing review separate from the SPI NOR addressing and programmed-device history topics linked below. Neither establishes EEPROM write inhibition. A useful candidate requirement identifies the protected scope, allowed read behaviour and applicable sampling boundary together. That states what the design needs without inventing a cancellation sequence, a security result or evidence that an actual board is currently protected.
Sources and further reading
Microchip document 21203R sections 2.4 and 6.3, with the adjacent write-operation explanation, were reread on 15 October 2026. Only full-array coverage, read/acknowledgement distinctions and STOP sampling are used; no pin map, security, erase or cancellation procedure is inferred.