As per SAP Help on Telegram Repetition and Channel Check

Synchronization means that after a connection was established by SAP EWM, the programmable logic controller (PLC) was given the opportunity to send all messages that accumulated during the period of disconnection.

PLC Sim emulator does not send telegrams if SAP EWM MFS communication channel is not started and not connected to the simulator. In fact the SEND button is disabled unless SAP EWM MFS is connected

Therefore it is recommended to switch off the channel synchronization while working with the emulator. That can be set up in SPRO SCM Extended Warehouse Management -> Extended Warehouse Management -> Material Flow System (MFS) -> Master Data -> Define Communication Channel

Nevertheless it is perfectly possible to simulate and test synchronization scenarios with the emulator.

Channel synchronization with the PLC emulator

The synchronization process is implemented with 3 types of telegrams:

synchronization setup, SYES
synchronization start, SYBE
synchronization end, SYED

The demo uses the following styling of the telegrams

LIFE – red
SYES – orange
SYBE – yellow
SYED – blue
handshake request – bold font
handshake acknowledgment – italic font

That is set up with the following properties in the emulator configuration file:

Style.LIFE-R.=255,0,0,B
Style.LIFE-A.=255,0,0,I
Style.SYES-R.=255,128,0,B
Style.SYES-A.=255,128,0,I
Style.SYBE-R.=255,255,0,B
Style.SYBE-A.=255,255,0,I
Style.SYEN-R.=0,0,255,B
Style.SYEN-A.=0,0,255,I

First, I have activated the synchronization for the LMS1 CONSYS 1 communication channel. The channel is stopped

Now, the channel is started from /SCWM/MON, node Material Flow System -> Communication Channel. The channel status is set to A indicating synchronization being executed. That sends the SYES telegram from SAP EWM MFS

Next, the SYBE telegram is sent to SAP EWM MFS indicating the beginning of the synchronization

The communication channel status is not changed by the SYBE telegram, as it is only the beginning of the synchronization. The synchronization is concluded with the SYEN telegram sent to SAP EWM MFS