Modbus communication can be Enhanced Intelligent performed in either RTU or ASCII Communication Module mode. The parallel port provides a The Model 4119A Enhanced Intelligent Centronics interface to a printer. Communication Module (EICM) allows the Tricon to communicate with Each EICM supports an aggregate data Modbus masters and slaves, TriStation rate of 57.6 kilobits per second (for all 1131, and printers. four serial ports). For Modbus connections, the EICM Programs for the Tricon use variable user can select the RS-232 point-to- names as identifiers but Modbus point interface for one master and one devices use numeric addresses called slave, or the RS-485 interface for one aliases. Therefore an alias must be master and up to 32 slaves. The RS-485 assigned to each Tricon variable name network trunk can be one or two that will be read by or written to a twisted-pair wires up to a maximum of Modbus device. An alias is a five-digit 4,000 feet (1,200 meters). number which represents the Modbus message type and the address of the Each EICM contains four serial ports variable in the Tricon. An alias number and one parallel port which can operate is assigned in TriStation 1131. concurrently. Each serial port can be configured as a Modbus master with up Any standard Modbus device can to seven Modbus masters per Tricon communicate with the Tricon through chassis. A single Tricon system the EICM, provided that aliases are supports a maximum of two EICMs, assigned to the Tricon variables. Alias which must reside in one logical slot. numbers must also be used when host (The hot-spare feature is not available computers access the Tricon through for the EICM, though you can replace a other communication modules, such as faulty EICM while the controller is the NCM. See “Communication Capa- online.) Each serial port is uniquely bilities” on page 61 for more informa- addressed and supports either the tion. Modbus or TriStation interface. EICM Specifications Model Number 4119A, Isolated Serial ports 4 ports RS-232, RS-422 or RS-485 Parallel ports 1, Centronics, isolated Port isolation 500 VDC Protocol TriStation, Modbus Modbus functions supported 01 — Read Coil Status 02 — Read Input Status 03 — Read Holding Registers 04 — Read Input Registers 05 — Modify Coil Status 06 — Modify Register Content 07 — Read Exception Status 08 — Loopback Diagnostic Test 15 — Force Multiple Coils 16 — Preset Multiple Registers Communication speed 1200, 2400, 9600, or 19,200 Baud Diagnostic Indicators Pass, FaULT, Active TX (Transmit) — 1 per port RX (Receive) — 1 per port 29