Replacing an I⁄O Module With a Hot Spare

Date: Mar 25, 2025 Views: 599

　　If the fault indicator of an I⁄O module is on, the diagnostics have detected a module failure.

　　To replace an I⁄O Module:

　　If available, make a note of the diagnostic message, model, and serial numbers.

　　Before replacing an I⁄O module, observe the important instructions provided in the section called “Guidelines for Replacing Modules” on page 195.

　　On the faulty I⁄O module, verify that the Fault indicator is on and the Active indicator is off

　　Verify that at least one I⁄O module has an Active indicator on.

　　On the faulty I⁄O module, rotate the lock lever counter-clockwise until the module ejects from the baseplate.

　　Insert the replacement I⁄O module in the vacant slot and rotate the lock lever clockwise to draw the module into the baseplate.

　　Note：When replacing a module, you must use a #2 flat-blade screwdriver to lock or unlock the module. See the “Installing Modules” procedure on page 148.

　　The Pass indicator should go on within one minute.

　　The Active indicator should go on within one to two minutes. Then the Active indicator on the faulty module goes off.

　　If the module is not properly seated, the Lock indicator stays on. The Active indicator does not go on until the I⁄O module is properly seated and locked.

　　Contact the Triconex Customer Response Center to obtain a returned material authorization (RMA) number.

　　Return the module to Triconex for repair.

　　RS-485 Signal Descriptions

　　RS-485 signals are transmitted over a cable of twisted-pair-wires. The polarity of the 2-to-6-Volt differential between the two wires indicates whether the data is marking or spacing. If terminal A is negative with respect to terminal B, the line is marking. If terminal A is positive with respect to terminal B, the line is spacing. The maximum cable length is dependent on the wire used. For example, using 24- AWG twisted-pair wire, the maximum length is 1.2 kilometers (4000 feet), but can be extended using modems. The following table describes the RS-485 signals.

　　CM Baseplate Connectors

　　The CM Baseplate provides the following connectors and MAUs:

　　• Modbus RS-232/RS-485 serial connectors

　　• Ethernet 10BaseT Net1 connectors

　　• AUI 10-megabit Ethernet MAUs

　　• Ethernet 100BaseTX Net2 connectors

　　• MII Ethernet MAUs

　　• Debug connector

　　Modbus RS-232/RS-485 Serial Connector

　　Pin-out information for a Modbus serial connector is shown on page 206. The Modbus port, which is DTE-compatible, is configured using TriStation to operate in either RS-232 or RS-485 mode.

　　RS-232 Signal Descriptions

　　Spacing (on or 0) occurs when RS-232 signals are between +6 and +12 V DC; marking (off or 1) occurs when they are between –6 and –12 V DC. The maximum cable length is 15 meters (50 feet), but can be extended using modems. The following table describes the RS-232 signals.

　　RS-485 Signal Descriptions

　　RS-485 signals are transmitted over a cable of twisted-pair-wires. The polarity of the 2-to-6-Volt differential between the two wires indicates whether the data is marking or spacing. If terminal A is negative with respect to terminal B, the line is marking. If terminal A is positive with respect to terminal B, the line is spacing. The maximum cable length is dependent on the wire used. For example, using 24- AWG twisted-pair wire, the maximum length is 1.2 kilometers (4000 feet), but can be extended using modems. The following table describes the RS-485 signals.

　　RS-232 Modbus Serial Cable

　　The RS-232 Modbus serial cable is a standard null-modem cable used to link the Modbus connector on the MP Baseplate to a PC acting as the Modbus master. Cable pin-outs are shown below:

　　RS-485 Modbus Serial Cables

　　RS-485 Modbus serial cables are used for point-to-point and multi-point connections between an MP or CM and a Modbus master.

　　The first figure below shows a point-to-point connection between a Modbus master and one slave only. The second figure shows a multi-point connection which includes one Modbus master and 2 to 32 slaves.

　　The network trunk should consist of double twisted-pair wires. When the trunk consists of double twisted pairs, one pair serves as the output line for the Modbus master (input line to all slaves). The other pair serves as the input line to the Modbus master (output line from all slaves). When the trunk consists of a single twisted pair, it serves as both the output and input lines to the Modbus master and all slaves. The trunk accommodates up to 32 two-foot branches, without restriction on the distance between branches.The following figures show these connections as they should be made at the MP or CM.

　　When an MP or CM is a slave in a multi-point network, multiple transmitters connect to the same conductor. One transmitter can be active at any time; otherwise, the signal is distorted. Therefore, each node must be in the tristate (or off) mode. To set the tristate mode for the MP and CM, set the Handshake mode to Hardware using the Setup dialog box in TriStation’s Hardware Allocation screen.

　　Cable Selection

　　When selecting an RS-485 cable for your Modbus network, you should observe the following guidelines:

　　• Maintain a cable impedance of greater than or equal to 100 ohms.

　　• Supply a separate shield for each twisted pair.

　　• Use double twisted-pair networks to house the pairs in a single sheath or in separate sheaths.

　　• Use branch cable of the same quality as the trunk cable, but of less rigid construction. For example, use Belden 9182 (150-ohm) for the trunk and Belden 9729 (150-ohm) for the branches.

　　• Follow all applicable local codes.

　　• Terminate the cable in the characteristic impedance of the cable.

　　Cable Termination

　　RS-485 trunk cable termination (point-to-point or multi-point) greater than 200 meters (650 feet) requires termination at each end. Traditionally, resistors are connected to each end of the cable. This technique matches the cable impedance and prevents signal reflections which could cause data errors. However, this technique has the following three undesirable side effects:

　　• When no driver is active on the pair, the resistors pull the two wires together. Noise—even very low-level noise—can appear to be data when the wires are in this state.

　　• When a driver is active on the pair but not sending data, the resistors cause 33 mA of DC current to flow in the cable. This is an excessive load on the driver.

　　• When a driver is transmitting data over the cable, the resistors lower the signal level and consequently lower the immunity to noise.

　　A better technique for terminating the cable pair is to use an RC network and pull-up/pull-down resistors. This reduces power consumption and forces the pair to a valid data state when no driver is active.

3BHE032593R0001
3BHE031194R0001
3BHE031197R0001
3BHB009181P0001
3BHE031194R0001
S-093M 3BHB009885R0013
S-093M 3BHB009885R0063
S-097H 3BHB009885R0052
S-093H 3BHB009885R0005
S-093R 3BHB009885R5311
S-073N 3BHB009884R0021
S-097H 3BHB009885R0052
S-073N 3BHB009884R0021
S-093H 3BHB030478R0309
S-053M 3BHB012897R0003
S-073N 3BHB009884R0021
S-113H 3BHB018008R0003
More......

RELATED ARTICLE