Comtrol Modbus TCP User Guide - Manual (Page 12)

12 - Chapter 1. Introduction DeviceMaster UP Modbus/TCP User Guide: 2000447 Rev. I
Dual Master (Virtual Peer-to-Peer) - Write Mode
1.4.4.3. Dual Master (Virtual Peer-to-Peer) - Write Mode
Dual master (virtual peer-to-
peer) - write mode:
• The DeviceMaster UP
and PLC initiate only
write messages to each
other.
• The DeviceMaster UP
writes received serial
and/or Ethernet device
data directly into PLC
memory with minimal
latency.
• The PLC can write to
serial and/or Ethernet devices through the DeviceMaster UP with minimal latency.
• This mode provides the lowest possible Ethernet bandwidth usage and most efficient usage of PLC and
DeviceMaster UP processing power.
• Only raw/ASCII devices are supported in this mode.
• The DeviceMaster UP Receive Transfer mode is set to Master and Transmit Transfer mode is set to Slave.
1.4.4.4. Dual Master (Virtual Peer-to-Peer) - Read Mode (Dual Polling)
Dual master (virtual peer-to-
peer) - read mode (dual
polling):
• This is provided for
programmers who
strongly prefer polling.
• The DeviceMaster UP
and PLC initiate only
read messages to each
other.
• The PLC will poll for
received serial and/or
Ethernet device data.
• The DeviceMaster UP polls for transmit data to serial and/or Ethernet devices.
• This mode requires the highest possible Ethernet bandwidth usage and provides the least efficient usage
of PLC and DeviceMaster UP processing power.
• Only raw/ASCII devices are supported in this mode.
• The DeviceMaster UP Receive Transfer mode is set to Slave and Transmit Transfer mode is set to Master.