Using protected command interface

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

• If the meter shows zero, someone else owns the semaphore. You must wait for the semaphore to be available before sending a command.

• If the meter shows a nonzero number, you own the semaphore. 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 zero 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

   Command block	Register number
   Command	2039
   Semaphore	5
   Parameters	1

4. Monitor the meter response registers for validity and completion.

   Protected meter response example

   Meter response	Register number
   Status	2039
   Result	0
   Data	1

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