RS-485 Wiring Primer

7/29/2019 RS-485 Wiring Primer

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Rev C 6/07/04 This document is property of Spectracom Corporation. Page 1 of 21

95 Methodist Hill Drive Suite 500 Rochester, New York 14623

USA +1.585.321.5800 FAX: +1.585.321.5218 www.spectracomcorp.com

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RS-485 BUS WIRING PRIMER

Purpose: This document provides general and specific information for the use of RS-485 data to inter-connect Spectracom Master clocks to other equipment, including Wall Clocks, TimeTaps, Ethernet TimeServers and TimeBursts. This document also contains information on troubleshooting RS-485.

RS-485 OUTPUT USAGE

The RS-485 Output provides a continuous once-per-second time data stream in the selected format.RS-485 is a balanced differential transmission which offers exceptional noise immunity, long cable runs

and multiple loading. These characteristics make RS-485 ideal for distributing time data throughout a facility.The RS-485 Output can drive 32 devices over cable lengths up to 4000 feet.

Spectracom manufactures wall clocks, RS-485 to RS-232 converters and radio link products whichutilize the RS-485 data stream as an input. Figures 1-1 and 1-2 illustrate typical RS-485 time data bus

inter-connections. Follow the guidelines listed below when constructing the RS-485 data bus.

TECHNICAL SUPPORT

For technical support, contact Spectracom Tech Support via phone or email at the address informationbelow. Tech Support is available Monday through Friday from 8:00 AM 5:00PM (Eastern).

Keith Wing: 585.321.5823

David Lorah: 585.321.5824

Receptionist: 585.321.5800

Fax: 585.321.5219

Email: [email protected]

http://www.spectracomcorp.com/
http://www.spectracomcorp.com/http://www.spectracomcorp.com/http://www.spectracomcorp.com/


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TABLE OF CONTENTS

SECTION 1: GENERAL RS-485 INFORMATION

1.0 Cable Selection

1.1 General Connection Information1.2 RS-485 Termination

SECTION 2: NTP TIME SERVERS (MODELS 8189, 918x series and TTSxxx series)

2.0 Remote Output2.1 Connection to a Wired Display Clock (Models 8175, 9175 or 9177)2.2 Connection to a TimeTap (Model 8179T)2.3 Connection to an Ethernet Time Server (Models 8188 or 9188)2.4 Connection to a TimeBurst (Model 8185)

SECTION 3: NETCLOCK/GPS MODEL 81833.0 Remote Output3.1 Connection to a Wired Display Clock (Models 8175, 9175 or 9177)3.2 Connection to a TimeTap (Model 8179T)3.3 Connection to an Ethernet Time Server (Models 8188 or 9188)3.4 Connection to a TimeBurst (Model 8185)

SECTION 4: NETCLOCK/2 MODEL 8182

4.0 Remote Output4.1 Connection to a Wired Display Clock (Models 8175, 9175 or 9177)4.2 Connection to a TimeTap (Model 8179T)4.3 Connection to an Ethernet Time Server (Models 8188 or 9188)4.4 Connection to a TimeBurst (Model 8185)

SECTION 5: TROUBLESHOOTING RS-485

5.0 Noticing a Problem with RS-4855.1 Termination Issue5.2 Time Synchronization of the Master Clock5.3 Verifying RS-485 with a Spectracom TimeTap5.4 Verifying RS-485 with an Oscilloscope.5.5 RS-485 Data is Present but Device still not Syncing5.6 Contacting Spectracom Tech Support for Assistance or RMA Number


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SECTION 1: GENERAL RS-485 INFORMATION

1.0 Cable Selection

Low capacitance, shielded twisted pair cable is recommended for installations where the RS-485 cablelength is expected to exceed 1500 feet. Table 1-1 suggests some manufacturers and part numbers forextended distance cables. These cables are specifically designed for RS-422 or RS-485 applications.They have a braided copper shield, nominal impedance of 120 ohms, and a capacitance of 12 to 16picofarads per foot.

RS-485 cable may be purchased from Spectracom. Specify part number CW04xxx, where xxx equals thelength in feet.

MANUFACTURER PART NUMBER

Belden Wire and Cable Company

1.800.BELDEN-1

9841

Carol Cable Company606.572.8000

C0841

National Wire and Cable Corp.323.255.5611

D-210-1

TABLE 1-1: Cable Sources for RS-485 Lines over 1500 Feet

For cable runs less than 1500 feet, a lower-cost twisted pair cable may be used. Refer to Table 1-2 forpossible sources.

MANUFACTURER PART NUMBER

Alpha WireCorporation1.800.52ALPHA

5471

Belden Wire andCable Company1.800.BELDEN-1

9501

Carol CableCompany606.572.8000

C0600

TABLE 1-2: Cable Sources for RS-485 Lines Under 1500 Feet


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1.1 General Connection Method

The RS-485 transmission line must be connected in a daisy chain configuration as shown in Figure 1-1.

In a daisy chain configuration, the transmission line connects from one RS-485 receiver to the next. Thetransmission line appears as one continuous line to the RS-485 driver.

A branched or star configuration is not recommended! This method of connection appears as taps orstubs to the RS-485 transmission line. Stub lengths affect the bus impedance and capacitive loadingwhich could result in reflections and signal distortion.

R S - 4 8 5O u t p u t

T e r m i n a lB l o c k

T i m e V i e w 2 3 0

T i m e V i e w 4 0 0 8 1 7 9 TT i m e T a p

8 1 8 8 / 9 1 8 8 T i m e S e r v e r

D I S P L A Y

D I S P L A Y RS-232 E T H E R N E T

1 0 /1 0 0 B A S E T

8 1 7 9 T

T i m e T a p

R S - 2 3 2

N e t C l o c k

D B 9

T e r m i n a l B l o c k

T E R M I N A T E E N D D E V IC E

T w i s t e dP a i r C a b l e

R S - 4 8 5T i m e D a t a B u s

T i m e T a p

R S 2 328 1 7 9 T

T e r m i n a l

B l o c k

R S - 4 8 5I n / Ou t

T e r m i n a l

B l o c k

R S - 4 8 5

I n / O u t

T e r m i n a l B l o c k

FIGURE 1-1: One-Way Bus Installation

The RS-485 Output may be split in two directions as shown in Figure 1-2. This allows the NetClock to becentrally located. Connecting in this method can simplify installation and possibly reduce the amount ofcable required.


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TimeBurst

TimeView 230 8188/9188 Time Server

8179T

TimeTap

NetClock

RS-232

DISPLAY ETHERNET10/100 BASE T

DIGITAL

MESSAGE8179T

TimeTap

RS-232

Terminal Block RS-485

Input

Terminal

Block

Terminal

Block

RS-485

Input

RS-485

Input/Output

TERMINATE

END DEVICE

Twisted Pair

Cable

RS-485

Time Data

TimeView 400

DISPLAY

RS-485

Input/Output

Terminal

Block

TERMINATEEND DEVICE

Terminal Block Terminal BlockTerminal

Block

FIGURE 1-2: Split Bus Configuration

Most RS-485 connections found on Spectracom equipment are made using a removable terminal strip.Wires are secured by a jaw which compresses the wires when tightened. When using small diameterwire, 22-26 gauge, a strain relief can be fashioned by wrapping the stripped wire over the insulating jacketas shown in Figure 1-3. Wrapping the wires in this manner prevents smaller gauge wires from breakingoff when exposed to handling or movement.

The Spectracom Models 8175 and 9175, TimeView 230, are a display clock with 2.3 inch high digits. The

Model 8177 TimeView 400 features 4.0 inch display digits. TimeView display clocks use a 6-positionterminal block to connect to the RS-485 data bus. Spectracom Model 8185, TimeBurst, is an audiointerface to a transmitter. The Spectracom Models 8188 and 9188 are Ethernet Time Servers. Thesedevices use a 3-position terminal block to connect to the RS-485 data bus. Connect all of these devicesto the Remote Output as shown in Figure 1-3.


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INSERT AND

TIGHTEN

STRIP

WIRE

WRAP WIRE OVER

INSULATING JACKET

FIGURE 1-3: WIRE STRAIN RELIEF

1.2 RS-485 Termination

A termination resistor is required on devices located at the ends of the RS-485 transmission line.Terminating the cable end preserves data integrity by preventing signal reflections. If there is only onedevice connected to the Remote port, it is considered the last device and should be terminated.

For a one-way bus installation (shown in Figure 1-1), terminate the last device on the bus. The RS-485data bus can be split in two directions at the clock itself (shown in Figure 1-2). In a split busconfiguration, terminate the devices installed on each end of the two buses. More than two lines out ofthe Netclock are not allowed. Never branch off in the middle of the line from one device to twoother devices! This can cause reflections in the bus.

Many Spectracom products include a built-in termination switch to terminate the RS-485 bus whenrequired. The Models 8175, 8177 and 8185 have a rear panel DIP switch used to terminate the clock if itis the last device on the line. The Model 8175 and 8177 termination switch is DIP switch number 10.The Model 8185 termination switch is DIP switch number 1.

The Models 9175, 8188, 9188 and 8179T do not have a built-in termination resistor. If one of thesedevices is at the end of the line, install the included 120 ohm resistor across the + Data and Data inputpins. This will terminate the end of the line.

NOTE:

Refer to Section 2 for instructions on connecting equipment the Remote port of the

Models 8189, 9189 or 9183. For the Netclock/GPS Model 8183, skip to Section 3.0.

for the Netclock/2 Model 8182, skip to section 4.0


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SECTION 2: NTP TIME SERVERS(MODELS 8189, 918x SERIES AND TTSxxx SERIES)

2.0 Remote Outputs

The Models 8189, 9188, 9189, TTS200 and TTS260 have one Remote Output labeled RS-485 1 (TheModels 9188 and TTS260 Remote ports labeled RS-485 2 are an input port from the Master clock). TheModel 9183, TTS220 and TTS240 have two Remote Outputs labeled RS-485 1 and RS-485 2. Theseoutputs provide a continuous once-per-second time data stream in the selected data format. There arefive time data format selections and one position data stream in NMEA 0183 format available. Refer tothe corresponding Master Clock instruction manual for a complete description of the Data Formatstructures and RS-485 output port descriptions.

In addition to Data Formats, baud rate and UTC time difference of each output is selectable. The Remoteoutput ports (With the exception of the Model 8189) are configured using the web browser interface forthe clock. Refer to the corresponding instruction manual for configuring these ports.

A 3-position terminal block is supplied in the ancillary kit for each Remote Connector. Connector pinassignments are shown in Figure 2-1.

RS-485 REMOTE

PORT 1 PORT2

FIGURE 2-1: Remote Outputs

RS-485 is a balanced differential transmission requiring twisted pair cabling. RS-485 characteristics makeit ideal to distribute time data throughout a facility. Each Remote Output can provide time to 32 devices atcable lengths up to 4000 feet. Refer to Figure 2-2 for a schematic representation of each RS-485 outputdriver. Relative to RS-485 specifications, the A terminal (Pin 2) is negative with respect to the B terminal

(Pin 1) for a mark or binary 1. The A terminal is positive to the B terminal for a space or binary 0.


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1

2

3

B

A

B Terminal (+)

A Terminal (-)

Shield

FIGURE 2-2: RS-485 Output

Spectracom offers many devices that accept the RS-485 data stream as an input reference. Theseproducts include display clocks, RS-485 to RS-232 converters, NTP time provider, and radio link productsto meet various time applications and requirements. For information on Remote Output usage refer toSection 1.0 of this document.

2.1 Connection to a Wired Display Clock

The Spectracom Models 8175 and 9175, TimeView 230, are a display clock with 2.3 inch high digits. TheModel 8177 TimeView 400 features 4.0 inch display digits. TimeView display clocks use a 6-positionterminal block to connect to the RS-485 data bus. Connect the TimeView to the Netclock Output asshown in Figure 2-3. The TimeView display clocks accept only Data Formats 0 or 1.

Spectracom display clocks have a built-in RS-485 repeater that can drive 32 more devices when theoutput connector is used. Either daisy chain the display clock inputs together OR run the bus wire fromthe output of one clock to the input of the next device. Because this ends the first bus, and starts another

bus, terminate this display clock as well as the last clock on the new line.

FIGURE 2-3: TimeView RS-485 Interface

Note: If pins 4 through 6 are

used, terminate the wall

clock.


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2.2 Connection to a TimeTap

The Model 8179T, TimeTap, is an RS-485 to RS-232 converter. The Model 8179T has a DB9 RS-232

interface that receives operational power from the RS-232 flow control pins RTS or DTR. Connect theTimeTap to the RS-485 data bus as shown in Figure 2-4.

FIGURE 2-4: Model 8179T TimeTap RS-485 Interface

2.3 Connection to an Ethernet Time Server

Spectracom Models 8188 and 9188, NetClock/ETS and Netclock/NTP are Ethernet Time Servers thatsupport NTP and SNTP time protocols. The Models 8188 and 9188 accept either Data Format 0 or 2 andconnect to the RS-485 data bus through a three-position terminal block. Connect the Models 8188 and9188 to the Master Clock as shown in Figure 2-5.

FIGURE 2-5: Model 8188 or 9188 RS-485 Interface


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2.4 Connection to a Model 8185 TimeBurst

The Model 8185, TimeBurst, provides a digital time-of-day data burst to a radio transmitter. The

TimeBurst, when used with the Spectracom Model 8186 TimeBridge, provides community-wide timesynchronization from a single NetClock. The TimeBurst accepts only Data Format 0. Connect theTimeBurst to the RS-485 data bus using a 3-position terminal block as shown in Figure 2-6.

FIGURE 2-6: TimeBurst RS-485 Interface


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SECTION 3: NETCLOCK/GPS MODEL 8183

3.0 Remote Outputs

The NetClock/GPS Model 8183 has two Remote Outputs labeled RS-485 1 and RS-485 2. Theseoutputs provide a continuous once-per-second time data stream in the selected data format. There arefive time data format selections and one position data stream in NMEA 0183 format available. Refer tothe Model 8183 instruction manual for a complete description of the Data Format structures.

In addition to data formats, baud rate and UTC time difference of each output is selectable. Thecommands REM1and REM2configure the ports setup. Refer to section 4 of the instruction manual for acomplete description of these commands.

A 3-position terminal block is supplied in the ancillary kit for each Remote Output. Connector pinassignments are shown in Figure 3-1.


RS-485 is a balanced differential transmission requiring twisted pair cabling. RS-485 characteristicsmake it ideal to distribute time data throughout a facility. Each Remote Output can provide time to 32devices at cable lengths up to 4000 feet. Refer to Figure 3-2 for a schematic representation of eachRS-485 output driver. Relative to RS-485 specifications, the A terminal (Pin 2) is negative with respectto the B terminal (Pin 1) for a mark or binary 1. The A terminal is positive to the B terminal for a space orbinary 0.


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1

2

3

B

A

B Terminal (+)

A Terminal (-)

Shield

FIGURE 3-2: RS-485 Output

Spectracom offers many devices that accept the RS-485 data stream as an input reference. Theseproducts include display clocks, RS-485 to RS-232 converters, NTP time provider and radio link productsto meet various time applications and requirements. For information on Remote Output usage refer toSection 1.0 of this chapter.

3.1 Connection to a Wired Display ClockThe Spectracom Models 8175 and 9175, TimeView 230, are a display clock with 2.3 inch high digits. TheModel 8177 TimeView 400 features 4.0 inch display digits. TimeView display clocks use a 6-positionterminal block to connect to the RS-485 data bus. Connect the TimeView to the NetClock/GPS RS-485Output as shown in Figure 3-3. The TimeView display clocks accept only Data Formats 0 or 1.

Spectracom display clocks have a built-in RS-485 repeater that can drive 32 more devices when theoutput connector is used. Either daisy chain the display clock inputs together OR run the bus wire fromthe output of one clock to the input of the next clock. Because this ends the first bus, and starts another

bus, terminate this display clock as well as the last clock on the new line.




clock.


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The Model 8179T, TimeTap, is an RS-485 to RS-232 converter. The Model 8179T has a DB9 RS-232interface that receives operational power from the RS-232 flow control pins RTS or DTR. Connect theTimeTap to the RS-485 data bus as shown in Figure 3-4.



Spectracom Models 8188 and 9188, NetClock/ETS and Netclock/NTP are Ethernet Time Servers thatsupports NTP and SNTP time protocols. The Models 8188 and 9188 accept either Format 0 or Format 2

and connect to the RS-485 data bus through a three-position terminal block. Connect the Model 8188 or9188 to the Netclock/GPS as shown in Figure 3-5.

FIGURE 3-5: Models 8188 or 9188 RS-485 Interface


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The Model 8185, TimeBurst

, provides a digital time-of-day data burst to a radio transmitter. TheTimeBurst, when used with the Spectracom Model 8186 TimeBridge, provides community-widetime synchronization from a single NetClock/GPS. The TimeBurst accepts only Format 0.Connect the TimeBurst to the RS-485 data bus using a 3-position terminal block as shown inFigure 3-6.



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SECTION 4: NETCLOCK/2 MODEL 8182

4.0 Remote Output

The Model 8182 has one Remote Port which is labeled Remote Output. This port provides a continuousonce-per-second time data stream in the selected data format. There are two time data format selectionsavailable (Data Format 0 and 1). Refer to the Netclock/2 instruction manual for a complete description ofthe Data Format structures.

In addition to Data Formats, baud rate and UTC time difference of this output is selectable via DIPswitches and rotary switches on the bottom cover of the Netclock/2. Refer to the Netclock/2 instructionmanual for configuring this port.

Connector pin assignments are shown in Figure 4-1 and Figure 4-2.

FIGURE 4-1: Remote Output Pin Numbering

PIN SIGNAL DESCRIPTION

38 -DATA+DATA RS-485 inverted time dataRS-485 non-inverted time data

27

-ON-TIME+ON-TIME

RS-485 inverted on-time pulseRS-485 non-inverted on-time pulse

16

-TSYNC+TSYNC

RS-485 inverted time sync statusRS-485 non-inverted time sync status

49

ENABLEGND

+5V Enable outputSignal Ground

5 TDATA RS-232 time data output



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Time data is broadcast in ASCII once-per-second in RS-485 levels, DATA, and at RS-232 levels,TDATA. Bit rate and Data Format selection are made by switches located on the bottom cover.The +ON-TIME signal is a positive-going 0.1 second pulse relative to -ON-TIME, occurring once per

second. The source of this output is the same as the 1-PPS output. Refer to Section 3.2.7 for additionalinformation about the on-time pulse output.

The +TSYNC signal is high relative to -TSYNC whenever the front panel TIME SYNC lamp is green.If the TIME SYNC lamp is red, the -TSYNC is high relative to the +TSYNC signal. The ENABLE signalis +5 volts through a 68-ohm series resistor.

Spectracom offers many devices that accept the RS-485 data stream as an input reference. Theseproducts include display clocks, RS-485 to RS-232 converters, NTP time providers, and radio linkproducts to meet various time applications and requirements. For information on Remote Output usagerefer to Section 1.0 of this document.

4.1 Connection to a Wired Display Clock

The Spectracom Model 8175 and 9175, TimeView 230, are a display clock with 2.3 inch high digits. TheModel 8177 TimeView 400 features 4.0 inch display digits. TimeView display clocks use a 6-positionterminal block to connect to the RS-485 data bus. Connect the TimeView to the Netclock Output asshown in Figure 4-2. The TimeView display clocks accept only Data Formats 0 or 1.

Spectracom display clocks have a built-in RS-485 repeater that can drive 32 more devices when theoutput connector is used. Either daisy chain the display clock inputs together OR run the bus wire fromthe output of one clock to the input of the next clock. Because this ends the first bus, and starts anotherbus, terminate this display clock as well as the last clock on the new line.




clock.


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The Model 8179T, TimeTap, is an RS-485 to RS-232 converter. The Model 8179T has a DB9 RS-232interface that receives operational power from the RS-232 flow control pins RTS or DTR. Connect theTimeTap to the RS-485 data bus as shown in Figure 4-3.



Spectracom Model 8188 and 9188, NetClock/ETS are Ethernet Time Servers that supports NTP andSNTP time protocols. The Model 8188 and 9188 accepts either Format 0 or Format 2 and connects tothe RS-485 data bus through a three-position terminal block. Connect the Model 8188 and 9188 to theNetclock as shown in Figure 4-4.

FIGURE 4-4: Models 8188 or 9188 RS-485 Interface


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The Model 8185, TimeBurst, provides a digital time-of-day data burst to a radio transmitter. The

TimeBurst, when used with the Spectracom Model 8186 TimeBridge, provides community-wide timesynchronization from a single NetClock. The TimeBurst accepts only Data Format 0. Connect theTimeBurst to the RS-485 data bus using a 3-position terminal block as shown in Figure 4-5.



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SECTION 5: TROUBLESHOOTING RS-485

5.0 Noticing a Problem with RS-485

If the device being synchronized by the RS-485 data does not synchronize within the normal time framethat it is supposed to sync in, you will need to determine if the problem is related to the Netclock MasterClock, the RS-485 cable between the Master Clock and the device or the device itself. Timesynchronization of a device may be either intermittent or it may not sync at all.

The first thing to determine is whether any other device on the RS-485 bus is synchronized, or are alldevices on the bus unsynchronized. If all devices are unsynchronized, the problem is most likely with theMaster Clock or a device loading down the bus. If all other devices are synced, the problem is most likelywith that particular device or a cabling issue between this device and the device that is immediatelybefore this device.

5.1 Termination Issue

If synchronization of one or more devices is intermittent or not occurring at all, determine if thetermination of the RS-485 bus is correct. Make sure the last device is correctly terminated into 120 ohmsas described in the procedure above and there are no branches from one device to two or more otherdevices (Branched or starred configurations are not acceptable). If the RS-485 bus is not properlyterminated or a branched or starred configuration is used, reflections may be occurring in the line causingloss of time sync. Correct the termination issue prior to proceeding with this section.

5.2 Time Synchronization of the Master Clock

If Time Synchronization of a device to the Master Clock does not occur, the problem may be due to theMaster Clock not being properly Time Synced. If the Master Clock is not synced, a Time Sync Statuscharacter in the data-stream will indicate to the device that the source is not synced. In most cases, thedevice will ignore the time stamp and remain unsynchronized. Verify the Time Sync lamp on the MasterClock indicates the Master Clock is synced. If it isnt, refer to the instruction manual for the specific modelMaster Clock or contact Tech Support for assistance.

5.3 Verifying RS-485 with a Spectracom TimeTap

The Spectracom TimeTap (Model 8178T or 8179T) is a good troubleshooting device to determine if RS-485 data is present. If a TimeTap is installed on the line, or if you have an available TimeTap, connectthe TimeTap to the RS-485 following the instruction manual for the TimeTap. Connect the TimeTapdirectly to a PC running either HyperTerminal or Procomm, using the baud rate setting of the MasterClock and 8 bit, No start bit, 1 stop bit and flow control set to hardware (Note that HyperTerminal requiresyou to do a Call and Disconnect then a Call and Connect or Call and Call before the new baudrate and settings are used). A readable ASCII data stream should be shown on the monitor everysecond. If the data is present and readable every second, the RS-485 output of the Master Clock and thewiring to that point is ok. If it is showing unreadable characters, the RS-485 + and - Data lines arebackwards and if it isnt present at all, either the RS-485 is bad or there is a setup issue on the PC.


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To verify a Spectracom Model 8178T TimeTap or 8179T TimeTap has a proper output:

1. Connect the TimeTap into the serial port of a laptop computer. A standard DB9 to DB25 adapter maybe required with an 8178T TimeTap.

2. Using the terminal emulator screen, you should see a line on your screen every second that lookssimilar to one of the three samples below (Depends on the selected Data Format).

A. 306 13:23 STZ=05 (Data Format 0)

B. THU 11NOV99 13:23:36 (Data Format 1)

C. 99 315 18:36:14.267S (Data Format 2)

Note:

If there is a ? or * at the beginning of the line, the Master Clock is not time synced.

Contact Spectracom Customer Service for assistance.

5.4 Verifying RS-485 with an Oscilloscope.

Due to the frequency response of a multi-meter, RS-485 is very difficult to measure with this testequipment. To correctly identify whether RS-485 is present, use an oscilloscope or a service monitor toview the signal. The + and Data should look similar to the Figure 5 below. The + and Data lines aresimilar but just inverted from each other. The location of the signal compared to ground does not matter

as RS-485 data is not based on differences between data and ground. Attenuated or distorted dataindicates the Master Clocks Remote port output is bad or a device on the RS-485 is loading down theline. No data present indicates the RS-485 cable is broken or the Master Clock RS-485 Remote portoutput data is not present. Check the Master Clock RS-485 Remote output to see if the data is present atthis point. If it isnt , disconnect the bus and check the port again. If the data is present, a device isloading down the bus. Disconnect each device one at a time until the bad device is located. If the dataisnt present, the Master Clock output is bad and the Master Clock needs to be returned for repair.Contact Tech Support for an RMA number. Refer to section 5.5 Contacting Spectracom Tech Supportfor assistance or RMA number.

FIGURE 5: RS-485 data viewed with an oscilloscope


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5.5 RS-485 Data is Present but Device is still not Syncing .

If the RS-485 signal shown in figure 5 above is present and the device is still not synchronized to theMaster Clock, one of the following is the cause of the problem:

1) Not enough time may have elapsed since connecting RS-485 to the device (Not all devices will syncimmediately. Refer to the vendor of the equipment to determine their time sync interval).

2) The Master Clock is not synced.

3) The RS-485 + Data, -Data and ground are not pinned correctly to the device.

3) The device may not be properly configured for the correct baud rate and Spectracom Data Format asselected in the Master Clock.

4) There is a problem with the device to be synchronized by the clock. Refer to the vendor of theequipment for additional information on their product.

5) Some devices need external time synchronization to be enabled (Typically in a configuration menu).External time sync may not be enabled in the device. Contact the vendor for additional information.

5.6 Contacting Spectracom Tech Support for Assistance or RMA number

For additional troubleshooting assistance or to return Spectracom equipment for evaluation/repair,contact Spectracom Tech Support. An RMA Number (Return Authorization Number) must be obtainedprior to returning any equipment to Spectracom for repair. Tech support is available Monday throughFriday from 8AM until 5PM Eastern.

RS-485 Wiring Primer

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