Here it is mentioned that the controller will be in a logical sleep state?
If the hardware doesn't support this sleep mode, then how will this logical sleep state be achieved? What is meant by logical sleep state?
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1\$\begingroup\$ Welcome to StackOverflow! Please take the tour to learn how this site works, and read "How to Ask". Then come back and edit your question to clarify, do not post comments, this is not a forum. -- Where is this requirement from? What controller do you mean? Did you ask the author of the requirement? If not, why not? The source documents should also define the terms "sleep mode", "SLEEP state", "logical SLEEP state" (I don't see "logical sleep mode" in the requirement), and "STOPPED state". If it does not, did you complain? If not, why not? \$\endgroup\$– the busybeeSep 20 at 5:43
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1\$\begingroup\$ It's actually a good question. \$\endgroup\$– VelvetSep 20 at 6:31
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\$\begingroup\$ Except the kind of applications where you find CAN are typically not extreme low current-consumption ones, but rather high integrity ones. \$\endgroup\$– LundinSep 20 at 7:01
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\$\begingroup\$ this is actually answered by reading the paragraph before your current paragraph closely! \$\endgroup\$– Marcus MüllerSep 20 at 9:58
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Source: AUTOSAR: Specification of CAN Driver
So this describes how a driver should behave towards the software using it.
Then that whole paragraph makes sense:
Your document (read it from the beginning) explicitly demands that your driver represents a state machine with the UNINIT, STOPPED, STARTED and SLEEP.
The sentence before the sentence that you cropped out is just as important:
[SWS_Can_00257] ⌈ When the CAN hardware supports sleep mode and is triggered to transition into SLEEP state, the Can module shall set the controller to the SLEEP state from which the hardware can be woken over CAN Bus.⌋ (SRS_SPAL_12067)
So, clearly, when the hardware supports a sleep state, there's a way of leaving that SLEEP state to the STARTED state, when the hardware receives a waking event from the bus.
Now, if the hardware doesn't support it, what are the possible state transitions?
SWS_Can_00258] ⌈ When the CAN hardware does not support sleep mode and is triggered to transition into SLEEP state, the Can module shall emulate a logical SLEEP state from which it returns only, when it is triggered by software to transition into STOPPED state.⌋ ()
So, in that case, there's no way to wake up the CAN through hardware, and the only possible state transition that can be done in software is to STOPPED.
Pretty straightforward! If it helps, draw yourself a finite state machine diagram (excerpt) for this. The only arrow between SLEEP and STARTED is a hardware wakeup, and there's an arrow from SLEEP to STOPPED which can be walked through a software command.
answered Sep 20 at 9:57
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\$\begingroup\$ Thank you for your time. But I still didn't understand what they meant by logical sleep state and it is mentioned that if hardware doesn't support it it will emulate a logical sleep state. So how are they achieving this sleep state? \$\endgroup\$– SUPERPIESep 20 at 11:17
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1\$\begingroup\$ there's nothing about "achieving" it. Your driver needs to represent a state machine. You simply change into the state called "SLEEP". It's a state of the driver, not the hardware! \$\endgroup\$ Sep 20 at 11:24
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1\$\begingroup\$ A CAN transceiver in a true sleep state does not participate in CAN communication (i.e. ACK-ing). What this AUTOSAR manual describes as "emulating a logical sleep state" isn't emulating anything. It is just an instruction for a workaround. \$\endgroup\$– VelvetSep 20 at 11:38