Commreq Example - Modbus Tcp Channels - GE PACSystems RXi User Manual

Chapter 8. Gigabit Ethernet (GbE) Interface Overview and Operation
8.7.3 COMMREQ Example – Modbus TCP Channels
The input values for the Block Move Functions in this example are taken from the Open
Modbus TCP Connection (3000), Modbus TCP Read (3003), and Close Modbus TCP
Connection (3001) examples in this chapter.
Named variables are used in this example to make the ladder program easier to follow.
LAN_IF_OK is bit 16 of the LAN Interface Status bits. LAN_OK is bit 13 of the LAN Interface
Status bits.
Rung #1: Input LAN_IF_OK (bit 16 of the LAN Interface Status bits) monitors the health of
the Ethernet interface. Input LAN_OK (bit 13 of the LAN Interface Status bits) monitors the
online/offline status of the Ethernet interface. If both bits are set, it is OK to send a
COMMREQ and the ETH_READY coil is ON. ETH_READY is used as an interlock for Rungs
2-16.
Rung #2: When ETH_READY is set, Input DO_OPEN triggers OPEN_REQ, which enables
execution of the MOVE and COMMREQ functions for the Open Modbus TCP Connection
COMMREQ. OPEN_REQ is a one-shot (Positive Transition) coil, activating once when both
ETH_READY and DO_OPEN have transitioned from OFF to ON.
182 PACSystems* RXi Distributed IO Controller User Manual GFK-2816F