083730300A DCN8101 Communications and Remote Operation 85
3.4 COMMUNICATIONS PROTOCOLS
MODBUS (Section 3.4.1) and Hessen (Section 3.4.2) are available with the analyzer.
MODBUS registers are provided in Appendix A.
3.4.1 MODBUS
These instructions assume that the user is familiar with MODBUS communications, and
provide minimal information to get started. Please refer to the Teledyne API MODBUS
manual, PN 06276, and to www.modbus.org for MODBUS communication protocols.
Minimum Requirements:
• Instrument firmware with MODBUS capabilities installed
• MODBUS-compatible software (TAPI uses MODBUS Poll for testing; see
www.modbustools.com)
• Personal computer with communications cable (Ethernet or USB or RS232), and possibly a
null modem adapter or cable
3.4.1.1 MODBUS COM PORT CONFIGURATION
MODBUS communications can be configured for transmission over Ethernet or serial
COM port through the Setup>Comm menu. Make the appropriate cable connections
(Ethernet or COM port) between the instrument and a PC.
Check the instrument’s Modbus Units selection in the Setup>Vars menu and edit if
needed.
Ethernet: MODBUS is available on TCP port 502. By default, port 502 is assigned to
the instrument’s TCP Port 2. (Setup>Comm> TCP Port2, Figure 3-1).
Figure 3-1. MODBUS via Ethernet
Serial COM: Both COM1 (labeled “RS232” on the instrument’s rear panel) and COM2
are configurable for RS-232 or RS-485 communication with either
MODBUS RTU or MODBUS ASCII transmission modes. In the
Setup>Comm COM1[COM2] menu, edit the Protocol parameter to select a
MODBUS transmission mode; edit Baud Rate, Parity, Data Bits, etc., if
necessary (see descriptions in Table 2-18).
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