In the PM5000 series meters, what is the difference between the protected and unprotected command interface?

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When sould registers 5000 - 5249 be used over 5250 - 5499?
Any examples will be very helpful!

[Usha · Accepted solution]

Hi Darell,

Protected mode requires the user to obtain the semaphore before executing the command.  PM5000 supports both protected and unprotected command interfaces.  In the register list, there is a "Commands" tab.  In that tab, it lists all of the commands that can be executed by the meter under protected or unprotected mode.  It also lists the parameters that need to be specified by each command.  You can filter those commands based on the column titled: "Allowed for Unprotected Command Interface".
Registers 5000-5249 are "Protected Command Interface" registers
Registers 5250 - 5499 are "Unprotected Command Interface" registers

Using the Protected Command Interface

To issue a meter command using the protected command interface, you must have a

command semaphore.

To get a semaphore, read the semaphore Modbus register. The power meter will return a 0 or a nonzero number.

• If 0 is returned, someone else owns the semaphore. You must wait for the semaphore to be available before sending a command.

• If a nonzero number is returned, you now own the semaphore. The semaphore is provided once until it is released or has been inactive for approximately 4 minutes.

Once you have the semaphore, subsequent reads of the semaphore register will return 0 until you release the semaphore or it times out.

To send a meter command using the protected command interface:

1. Read the semaphore register and record the meter response. This is your semaphore.

2. Build the packet to be written to the command block.

3. Write the packet as a Modbus block write (enter the command number, semaphore,

and parameters at the same time).

Protected Command Block Example

4. Monitor the meter response registers for validity and completion

Protected Meter Response Example

5. Write the semaphore back to the semaphore register to release it for another master to use.

Using the Unprotected Command Interface

The unprotected command interface allows you to issue a broadcast command to multiple meters at once. The unprotected command interface ignores the semaphore register.

Although some applications require the unprotected command interface, it is recommended that you use the protected command interface whenever possible.

To send a meter command using the unprotected command interface:

1. Build the packet to be written to the command block.

2. Write the packet as a Modbus block write (enter the command number, any number

as the semaphore, and the parameters at the same time).

Unprotected Command Block Example

3. Monitor the meter response registers for validity and completion

Unprotected Meter Response Example

[sesa277735]

Hey Usha M R,

Thanks for taking the time to answer my question!