real-time clock communications modules ......most real -time clock communication s module is...

ICS Regent® PD-6003

Industrial Control Services 1

Real-Time Clock Communications Modules

RS232 Communications and Battery-Backed Real-Time Clock

(T3151)

Issue 1, March, 06

Real-time clock communications modules provide a serial communications interface between the controller and external equipment. The module also provides battery-backed real-time information to the controller and applications programs. Real-time clock communications modules are recommended for applications that perform sequence of events recording or process historian data collection.

Features

• Battery-backed real-time clock.

· Date format: Month-day-year.

· Time format: Hours:minutes:seconds:milliseconds.

· One millisecond resolution.

· Two serial ports per module.

· Supports RS-232 standards.

· Hot Replaceable.

· Front panel indicators on each module show communications status and transmit/receive activity.

· TÜV certified for safety, Risk Class 5.

Module Operation

Figure 1 shows a block diagram of the real-time clock communications module.

Real-Time Clock Communications Modules (T3151)

2 Industrial Control Services

Each real-time clock communications module has a Z80 micro-processor, a PROM containing all of the module’s executable software, static RAM containing program variables, the real-time clock, shared RAM for transferring information between the processor modules and the communications module’s microprocessor, and a dual-channel UART with RS-232 serial port interfaces. Both the clock and the static RAM are battery-backed. If the system is powered down the battery continues to keep the clock running. The microprocessor reads the time, checks it for consistency, and then transfers it to the shared RAM where it can be read by the processor modules.

Each communications module receives power from all three of the processor modules. A power-sharing circuit in each of the communications modules receives the power from the three processor modules and combines it through a diode OR power-sharing circuit. This ensures that if one processor module's power supply fails, the communications module will continue to operate by drawing power from the two remaining power supplies, and the system's communications functions are maintained.

The Dual UART (universal asynchronous receiver/trans-mitter) buffers incoming and outgoing communications characters. The triplicated processor modules interrupt once every millisecond to read characters from or write characters to the communications module.


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Figure 1. Block Diagram of Real-Time Clock Communications Module.

When the processor modules read characters from the communications module, the communications module sends characters through triplicated bus drivers to the processor Safetybus. The processor modules vote this triplicated data and perform communications processing. When the processor modules write data to the communications module, the triplicated data is voted by the communications modules and sent to the dual UART where it is then transmitted out the associated port.

The communications modules’ two serial ports operate independently and can both be configured differently to support a wide variety of functions including Regent R2



protocol, Modbus protocol, ASCII output, and Guarded Peer-Link communications. The WINTERPRET application is used to configure the appropriate port functions and specify baud rate, data format, parity, and node number.

Once each application program scan the processors modules read the real-time clock data from the module. The real-time clock information is placed on the Safetybus from three independently controlled buffers, preventing failures in the real-time clock communications module from propagating into the system.

When the processor modules set the real-time clock, all real-time clock communications modules that are installed in the system are simultaneously set. After setting the real-time clocks, the processor modules read real-time clock values from the left-most installed communications module. If the left-most real-time clock communications module is faulted, the processor modules will then read real-time clock values from the next real-time clock communications module to the right.

Testing and Diagnostics

The modules triplicated Safetybus interface ensures that no failure in the module will effect the operation of the Regent system or other module. Extensive fault detection and annunciation of critical redundant circuits helps ensure that processors will not accept erroneous data from a faulty module.

Each type of communications module has a unique identification code that is read by the controller. This code lets the controller know what type of module is installed in each communications slot. If a module is removed and replaced with a module of a different type the processors will indicate a COMM error.

The processor modules perform background diagnostic checks on the module to test bus driver circuits and check the communications module ID codes. Clock values are checked for bad data. Communications message format, framing, checksum, and other communications errors are checked by the processor modules’ normal communications processing.


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Failures result in a COMM module error indication at the processor modules and an RTC/COMM error at the communications module.

Front Panel

Figure 2 shows the physical features of the real-time clock communications modules. The front panel of each module contains indicators showing overall module health, transmit and receive status, and backup battery power. In addition to the front panel indicators, each real-time clock communications module has two DB-25 serial ports.

RTC/COMM Indicator

This red and green LED pair indicates the overall health of the module. During normal operation the green LED is on. If a module fault occurs the red LED turns on and the green LED turns off.

Transmit/Receive Indicators

These green LEDs are connected directly to the RS-232 signal lines and flash while data are being transmitted or received. The TX LED flashes as data are sent from the module, and the RX LED flashes as data are received by the module.

Battery Status Indicator

This green LED is on when the battery is good and the module is installed in the controller chassis and is receiving power. This LED turns off if power is removed from the module, or if the battery runs low.



Figure 2. Real-Time Clock Communications Module.


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Application

Setting the Real-Time Clock

The real-time clock is set by loading the associated system variable registers with the desired time and date values and subsequently turning on the RTCSET system variable control relay. The WINTERPRET application can be used to perform this function using the Set Real-Time Clock command from the Project Editor’s Controller menu. This command opens the dialog shown in Figure 3. In the Set Real-Time Clock dialog enter the desired values for Month, Day, Year, Hour, Minute and Second (milliseconds are automatically set to zero when the clock is set). Choose OK to send the values to the Regent.

Figure 3. WINTERPRET’s Set Real-Time Clock Dialog.

By reading and writing to the real-time clock system registers, other communications equipment can read and set the real-time clock. The associated system variables are listed in Table 1. The “Set” values are sent to the real-time-clock communications modules when the system variable control relay RTCSET is turned on.



Table 1. Real-Time Clock System Registers.

Unit Read Clock Tag Name

Set Clock Tag Name

Year RTCYEAR SETYEAR

Month RTCMNTH SETMNTH

Day of Month RTCDOM SETDOM

Day of Week RTCDOW SETDOW

Hour RTCHOUR SETHOUR

Minute RTCMIN SETMIN

Second RTCSEC SETSEC

Millisecond RTCMS (always set to 0)

Communication Port Connections

Each communications port has a DB-25, female connector on the front of the module. The RS232 signals are internally connected to the DB-25 connector pins listed in Table 2.

Table 2. Communications Port Pin-out.

Signal Pin

TXD 2

RXD 3

GND 7

Typically these ports are used to connect to a communications device located within 150 feet of the system. For longer distances, external modems or signal converters may be used.

Since the module only provides RS232 interface connections, external signal converters (RS232 to RS422/485) are required if the module is to be connected in multidrop configurations. These configurations may include Guarded Peer-Link to other Regents or multidrop networks to a central PC, Man-Machine Interface or other communications devices (that support the Regent R2 or Modbus RTU protocols).


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Protocols and Communications Functions

The protocol and function supported for each port is configured using the Serial Ports command from the Project Editor’s Definitions menu in WINTERPRET. An example of the Serial Ports dialog is shown in Figure 4.

Figure 4. WINTERPRET’s Serial Ports Configuration Dialog.

The function and protocol for each type of port that you can select is briefly described below. For more information on using the Serial Ports command see Section 4, Working with Projects, in the Regent User’s Guide.

Only COMM, ASCII and MODBUS (point-to-point connection) can be directly interfaced to the real-time clock communications module. The other communications functions, which require multidrop connections, can be configured for the module but require an external signal converter to support the necessary RS422/485 multidrop network.

Comm

Supports the Regent R2 protocol for point-to-point communications between the Regent and the computer running the WINTERPRET application. Some third-party Man-Machine-Interface (MMI) products and DCS gateways may also support point-to-point communications using the Regent R2 protocol.

Note:


1 0 Industrial Control Services

Multidrop

Supports Regent R2 protocol for multidropped Regents connected to a PC running the WINTERPRET application (or other third-party supporting products and gateways). Ports configured for multidrop communications require a node number.

ASCII

Used by the Regent to transmit ASCII output messages to external serial equipment such as printers and VDUs. ASCII output messages are programmed using the ASCII output element in ladder logic function blocks.

Net Master/Net Slave

Used by the Regent for Guarded Peer-Link communications to other multidrop Regents. These ports require a node number.

Modbus

Supports connection to external Modbus communications equipment that acts as a Modbus Master (the Regent is a Modbus Slave). A Modbus port supports the Modbus RTU protocol. Modbus ports can be used in point-to-point or multidrop configurations. These ports require a node number.

Maintenance

Each real-time clock communications module has a replaceable lithium battery. The purpose of this battery is to provide sufficient backup power to keep the real-time clock running.

The battery used in the module has a shelf life of approximately 10 years. When providing power to the module's memory during a power failure, the battery can provide backup power to a real-time clock communications module's memory for approximately six months.

Battery Replacement

To replace the battery in a real-time clock communications module remove the module from the controller chassis and lay


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the module on its side so that the battery is accessible. See Figure 5.

Figure 5. Replacing a Real-Time Clock Communications Module Battery.



Disconnect the lead button connectors from the battery's positive and negative terminals. Carefully pull the battery from it retaining clip and remove the battery from the module.

Attach the battery lead button connector to the battery's positive and negative terminals. Do not use metal tools to install the battery lead button connector as they may short-circuit the battery. You should be able to install the connector without tools.

Carefully press the battery into the module’s battery retaining clip.

Reinstall the real-time clock communications module in the controller chassis and perform a voted reset to clear the fault indications.

Safety Considerations

Real-time clock communications modules are TÜV certified for Risk Class 5 safety applications as non-interfering and can be used in a safety system for normal data acquisition functions.

Real-time clock communications modules are approved for peer-to-peer communications of safety critical data between two or more Regent systems in Risk Class 5 safety applications. This requires the use of redundant Guarded Peer-Link communications networks where the network connections are made on redundant communications modules at each Regent.

For additional safety considerations involving communications with the Regent, refer to the Safety Considerations Section of the Regent User’s Manual.


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Specifications

Power Requirements No external power required (powered by triplicated processor modules)

Number of Serial Ports Two

Serial Port Type RS-232

Baud Rates 300 to 19,200

Communications Protocols Regent R2

Modbus RTU

ASCII Output

Guarded Peer-Link

Serial Port Connector Module: Cable:

DB-25, female DB-25, male

Real-Time Clock Resolution: Accuracy: Date: Time: Clock Set:

1 millisecond, read once per application program scan 20 to 40 ppm (10 to 20 minutes per year) Year, month, day of month, day of week Hour, minute, second, millisecond Communications device or application program

Battery Type Li/SO2

Battery Life Under Load: Shelf Life:

6 months 10 years

Isolation Serial signal ground is common with logic signal ground

Heat Dissipation 7 Watts, 24 BTUs/hour



Operating Temperature 0° to 60° C (32° to 140° F)

Storage Temperature -40° to 85° C (-40° to 185° F)

Operating Humidity 0 to 95% relative humidity, non-condensing

Vibration 10 to 55 Hz:

±0.15mm

Shock Operating:

15 g, ½ sine wave, 11 msec

Electromagnetic Interference

• IEC 801 Part 2 - Electrostatic Discharges

• IEC 801 Part 3 - Radiated Electromagnetic Fields

• IEC 801 Part 4 - Transients and Bursts

Level 3: Contact discharge of 6 kV

Level 3: 10 V/M, 27 MHz - 500 MHz

Level 4: 2 kV, 2.5 kHz for t = 60 sec

Safety Certified to DIN V VDE 0801 for Risk Class 5. Also designed to meet UL 508 and CSA 22.2, No. 142-M1981

Dimensions Height: Width: Depth:

13.0" (330 mm) 1.5" (38 mm) 9.0" (229 mm)

Weight 3.0 lbs (1.4 kg)

real-time clock communications modules ......most real -time clock communication s module is...

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