1. Separate standby from deep power-down
Microchip's SST26VF040A discussion distinguishes standby from deep power-down. The entry description begins from standby, and the release description returns the device to standby. These are named states with a transition between them, rather than interchangeable ways of saying the host is not currently reading. Preserve the requested state when comparing a memory's power-management behavior.
Command availability changes in the documented deep-power-down state. Microchip states that instructions are ignored there except for release from deep power-down. That makes the state relevant to functional access, not only a power description. A requirement expecting an ordinary memory operation must therefore identify whether the device is still asleep or has completed the transition needed for access.
The named example does not define every nonvolatile memory's sleep behavior. Another candidate needs its own state and command-availability description. Even for SST26VF040A, a general low-power feature heading would omit the distinction between a host that is idle and a device that has entered deep power-down. Start with the state the application actually requires.
2. Check whether the device can enter the requested state
The entry request has a condition: an internal write operation can cause it to be ignored. Microchip specifically describes program or erase activity as preventing entry into deep power-down. The existence of a transmitted sleep instruction is therefore insufficient evidence that the device changed state. Its ongoing internal activity belongs in the timing question. Two otherwise similar requests can therefore face different entry conditions: one concerns an idle device, while another overlaps an internal operation. Establishing which condition applies is logically prior to discussing the entry delay. A delay description cannot show that an ignored instruction was accepted.
An ignored request should not be rewritten as a promise of deferred automatic entry. The source's stated behavior is that the instruction does not place the busy device into deep power-down. This distinction matters when an application description assumes that requesting a lower-power state has already completed the transition, without identifying the operation that may still be active internally.
There is also an entry delay after the instruction's completion condition. Acceptance and arrival in the lower-power state are therefore separate events in the description. Keep both visible when framing the requirement. This guide assigns neither a delay value nor an instruction sequence; it identifies why a request event alone cannot establish the memory's subsequent state or consumption.
3. Separate release completion from access readiness
Release introduces another transition rather than making the memory immediately ready at the instant the host names the command. Microchip describes return to standby and readiness for the next instruction after a specified recovery interval. Preserve that distinction between completing the release instruction and reaching the state in which following access is permitted.
The same section discusses release together with reading the device ID. That identity-related function should not be expanded into a general claim that any next array access is already ready. Its description still retains the return-to-standby condition. The relevant selection question is what the application wants to do after release and which exact timing evidence covers that next operation.
Entry timing and release recovery answer opposite sides of the state change. A known entry delay does not supply the return delay, and the presence of a release function does not prove the earlier entry occurred. Treat the transitions individually. This keeps the application's state assumptions understandable without turning the description into a pin sequence, command code or universal wake-up recipe.
4. Frame a host sequencing requirement
A useful host requirement identifies the memory state before the request, any internal operation that could prevent entry and the first operation required after release. These are functional events, not a proposed implementation sequence. They allow the firmware reviewer to determine which state transition must be supported before assigning the appropriate device-specific timing conditions.
For example, requesting deep power-down while an internal erase remains active creates an entry-acceptance question. Releasing a device that is already asleep creates a recovery-readiness question. They should not share one undifferentiated sleep-time entry. The application must be able to distinguish the condition being assessed, even if both events appear within its wider power-management design.
This differs from NOR address reachability or programmable-logic configuration startup. Those earlier guides concern address state and configuration resources. Here the question is whether a named memory has entered or left a state that restricts instruction availability. Keep the relevant exact-device state description with the sourcing requirement. No boot result, firmware procedure, timing value or current saving on the customer's board is established here.
Sources and further reading
Microchip DS20006292A physical pages 38–39 were reread as saved text on 15 October 2026 for SST26VF040A entry and release behavior. No opcode, timing value, pin or clock sequence, waveform interpretation or universal memory sleep rule is supplied.