Model 4xx. Plug-in Series Of FSK Modems USER GUIDE. (TI) 20 Jan 06 DWG: A GDI COMMUNICATIONS LLC PO Box I-80 Exit 1 Verdi, NV 89439

Transcription

1 Model 4xx Plug-in Series Of FSK s USER GUIDE (TI) 20 Jan 06 DWG: A01164 GDI COMMUNICATIONS LLC PO Box I-80 Exit 1 Verdi, NV Phone: (775) Fax: (775) Web: support@sgdi.net

2 Contents Introduction to the 4xx Plug-in Series of s 3 Basics The Poll...5 The Response...6 View Card Edge Connector LED s Displays....8 RXD (Received Data)..8 DCD (Data Carrier Detect)..8 TXD (Transmit Data)...8 RTS (Request To Send) 8 CTS (Clear To Send) 8 DIP Switches 8 Full or Half Duplex..8 RTS to CTS Time.8 Soft Carrier Turn Off Time..8 Local Echo 8 Receiver Squelch Time 9 Carrier Detect...9 Anti-Streaming...9 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 1

3 Contents continued Data Protocol RS Applications Half Duplex Operation (2 Wire One Pair ) Full Duplex Operation (4 Wire Two Pairs) How to Add Fiber and Radio s To Your System..12 KOD Applications...13 More Applications...14 Repeater Applications A Word on Dynamic Range..16 Notes..17 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 2

4 TRODUCTION to the 4xx Plug-in Series of s Model 4xx Plug-in TOP OF BOARD RXD DCD TXD OFF RTS-CTS SOFT CAR ECHO------FULL REC SQLCH CAR DET ANTI-STR ON FULL DUPLEX HALF DUPLEX HALF DUPLEX RTS CTS The Model 4xx Plug-in Series is an asynchronous modem designed for RS232 communications over un-terminated private wire utilizing Frequency Shift Keying techniques (tones). The modems can communicate in 2 Wire Half Duplex or 4 Wire Full Duplex at baud rates up to 19.2Kbt/s depending on the model, all have adjustable timing parameters. The modems are typically deployed in a Point to Multi-point configuration such as TMC Master polling scheme that communicates with Remote Traffic Controllers. A typical system deployment of the modems would be in a R Rack at the Traffic Maintenance Center (Master End) and then communicating with remote modems (Slaves) embedded in the 170 Controllers. The same plug-in modem is used at both locations; all power and communications are provided by the host device, either the 170 Controller or the R Rack. The Rack is capable of housing 10 modems each communicating with there own string of modems. Please note the modem does not have a selectable identity, such as a Master or Slave and only assumes this identity depending upon where they are deployed. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 3

5 Basics The term is a combination of two words, Modulator and Demodulator. Frequency Shift Keying (FSK) s are designed to convert digital data to tone frequencies, this process is called modulation. The frequencies can easily be transmitted via a communication line to the receiving modem. At the opposite end of the communication line the tone frequencies are converted back to digital data by a process known as demodulation. By using this mechanism, two digital devices, such as Traffic Maintenance Center s (TMC) Computer and a Remote Controller can communicate with each other via the outside cable plant. Transmit Section of 1 Receive Section of 2 Digital Tones Digital Modulator Transmit Cable Pair Demodulator The 4xx series of modems use a modulation technique known as Frequency Shift Keying (FSK). Digital information is binary in format: that is, data is represented by either logic high or logic low (1 or 0). Communications terminology refers to logic Low as Mark and logic High as a Space. FSK s utilize this fact and generate a unique frequency for each logic level. Each model in the 4xx series have their own unique set of frequencies due to the baud rate therefore only modems of the same model number can communicate with each other, see the following chart. RS232 Model Number Input/Output Baud Rate Mark Frequency Low (0) 1200Hz 2400Hz 11200Hz 19200Hz Space Frequency High (1) 2200Hz 4400Hz 17600Hz 38400Hz Soft Carrier 900Hz 1800Hz 7800Hz 13800Hz The rate at which the communication line changes state is known as the baud rate, this can be interpreted to be equivalent of bits per second. The Model 4xx Series of Plug-in s are capable of communicating at baud rates up to 19.2Kbts depending on the model number. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 4

6 Communications Sequence of Events For ease of understanding this sequence of events we will limit our discussions to one modem at the TMC and one Remote modem connected to a Controller over a 4 wire system. Note; Transmit and receive pairs are referenced to the Master end of a 4 wire circuit, also a modem has a Transmit Section and a Receive Section. The Poll TMC Computer Master RTS CTS DATA Transmit Section Transmit Pair Receive Section CD DATA Remote Controller 1. The TMC computer (Master) signals the modem that it wants to transmit data by raising Request To Send (RTS) at the modems input. The modem returns a Clear To Send (CTS) back to the TMC computer after a time delay (user selectable). This is called Handshaking. As soon as the master modem sees RTS it transmits a Mark tone down the copper wire to wake up the remote modem. 2. The Remote s Carrier Detect (CD) circuit sees the Mark tone. If the tone is continuous for 4 or 8ms (user selectable) the Carrier Detect circuit will validate it and unlock the receivers output (removes Receiver Squelch) and raise CD at the data port. This CD signal advises the Controller to expect data. The demodulated Mark tone, logic 0, is passed to the RS232 Data port, where it does not change state due to the fact that when not in use it is always at logic 0, same as the transmit end. Now let s go back to the TMC end. 3. Once the TMC computer receives CTS (clear to send) it will send data to the modem. At this juncture both modems on the system are in a go state. 4. The TMC computer now sends data (0 s and 1 s) to the modem which converts it to Mark and Space frequencies. These frequencies (tones) are then transmitted down one pair of wires known as the transmit pair to the Remote modems receiver. When the data ends, RTS is lowered and the modem transmits a short burst of Soft Carrier (tone is out of band of the Mark/Space frequencies). This lower frequency tone causes the receiving modem to squelch the input to the digital circuits. This action closes the modems door to prevent noisy lines from false triggering the data circuits. The modem is now quiet. 5. We have now completed the Polling phase. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 5

7 The Response CD RTS TMC Computer DATA Receive Section Receive Pair Transmit Section CTS DATA Remote Controller 1. The Controller recognizes its address and prepares a message to be sent back to the TMC computer. Our response message will be sent back to the TMC on the Receive Pair of the 4wire system. 2. The Controller (Remote) signals the modem that it wants to send data by raising Request To Send (RTS) at the modems input. The modem returns a Clear To Send (CTS) back to the Controller after a time delay (user selectable). This is called Handshaking. As soon as the remote modem sees RTS it transmits a Mark Tone down the copper wire to wake up the Master modem. 3. The TMC s Carrier Detect (CD) circuit sees the Mark tone. If the tone is continuous for 4 or 8ms (user selectable) the Carrier Detect circuit will validate it and unlock the receivers output (removes receiver squelch) and raise CD at the data port. This CD signal advises the TMC computer to expect data. The demodulated Mark tone, logic 0, is passed to the RS232 Data port, where it does not change state due to the fact that when not in use it is always at logic 0, same as the Controller end. Now let s go back to the Controller end. 4. Once the Controller receives CTS (clear to send) it will send data to the modem. At this juncture both modems on the system are in a go state. 5. The Controller now sends data (0 s and 1 s) to the modem which converts it to Mark and Space frequencies. These frequencies (tones) are then transmitted down the receive pair of wires to the TMC modems receiver. 6. At the TMC modems receiver the Mark and Space frequencies are demodulated into 0 s and 1 s respectively. This is the same bit pattern that the Controller sent to the modem for transmission. This data is then sent to the TMC computer via the communication port. When the data ends, RTS is lowered and the modem transmits a short burst of Soft Carrier (tone is out of band of the Mark/Space frequencies). This lower frequency tone causes the receiving modem to squelch the input to the digital circuits. This action closes the modems door to prevent noisy lines from false triggering the data circuits. The modem is now quiet. 7. We have now completed the Response phase. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 6

8 View (Component Side) Card Edge Connector. TOP OF BOARD Pin Numbers are on the Component Side, Letters are on the solder side 1 This Side RXD DCD TXD RTS CTS LED S DIP Switches Card Edge Connector This is a standard 400 plug-in card size with 22 pins on each side, not all pins are used. SOLDER SIDE COMPONENT SIDE Letter Allocation by Pin Number Allocation by Pin Number Function Number 1 A Ground 2 B Ground 2 2 Audio In 3 C +12V 3 3 Audio In 4 D +12V 5 E -12V 6 F -12V 9 K DCD 10 L RTS 11 M TXD 12 N CTS 13 P RXD 20 X Audio Out 21 Y Audio Out Power Requirements are: 80ma at +12V 80ma at - 12V 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 7

9 LED s Displays The modem has five LED s that gives valuable information about the status of the modem and system operation. Received Data (RXD) (Output) This indicates data derived from the demodulated FSK signal from the far end modem and is routed to the serial port to be transmitted to the Host device. Data Carrier Detect (DCD) (Output) Indicates that the modem has detected a carrier tone from a far end modem. TXD (Transmit Data) (Input) This indicates data activity from the Host device into the modems serial port. RTS (Request To Send) (Input) Lights up when the attached Host device, TMC Digiport or Controllers serial port raises RTS, this is the first part of handshaking and causes the modem to wake up and transmit a Mark signal over the 2/4 wire cable system. RXD DCD TXD RTS CTS CTS (Clear To Send) (Output) The responds to the incoming RTS by raising CTS to the attached device after a selected delay of 6 or 12ms. This is the second and final part of handshaking protocol. Dip Switches REC SQLCH Full Duplex or Half Duplex CAR DET ANTI-STR The first two switches select whether the modem operates in Full Duplex (4 Wire) or Half Duplex (2 Wire) mode. RTS to CTS Time The delay time between the received RTS and the modems CTS response can be set to 12 or 6 ms. Soft Carrier Turn Off Time How long the carrier stays on after RTS is lowered. Local Echo 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 8 OFF RTS-CTS 12ms SOFT CAR 10ms ECHO------FULL Duplex 6ms 8ms ON 6ms 5ms 3ms 4ms FULL DUPLEX HALF DUPLEX HALF DUPLEX

10 Select OFF for Full Duplex and On for Half Duplex. Receiver Squelch Time The length of time which the Soft Carrier detector has before disabling the receivers output to the digital circuits; this can be set to 6 or 3ms. Carrier Detect The length of time after carrier has been detected before enabling the receivers output to the digital circuits; this can be set for 8 or 4ms. Anti- Streaming * Anti streaming is a feature that prevents a modem connected to a malfunctioning controller from monopolizing and jamming up the communications path. As an example, in multi-drop, polled, environments a Master sends out a logical address and expects a response from the addressed device. If another unaddressed controller has raised RTS, this will cause its attached modem to broadcast a carrier tone which will jam all the modems on the line. The Ant-Streaming feature of the modem prevents this by limiting the amount of time that the modem can continuously transmit to around 7 seconds. If Request To Send remains continuously active for longer than this period, the modem will override the condition, and stop transmitting until RTS goes Low. Data Protocol RS232 This is the standard format for the modem and is designed for short distance communications of less than 100ft and is ideal when connecting to the traffic controller or other devices within the cabinet. * Note: All Plug-in s have the Anti Streaming feature with the exception of the Model 400E. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 9

11 APPLICATIONS Half Duplex Operation (2 Wire One Pair ) TMC Host RS232 4xx Request Reply Request Reply 4xx 4xx In this mode the transmit path is shared with the receive path so only one modem at a time can be on the line. The far end modem has to wait until the Master modem has stopped transmitting before it can send a message back, therefore it is important to slow things down by setting the modems timing parameters to the longest times. This will result in a slower turn around time for the system. All modems on the 2 wire pair should be set with the same timing plan so as not to step over each other. Note that all 2 wire connections are made only to the terminals on all modems. To shorten up this round trip delay time and therefore speed up the system response it is necessary to go to a 4wire operation. The DIP Switch diagram below is where the adjustments are made to operate in either 2 or 4 wire mode, note also you can change various timing parameters. The settings shown are for 2 Wire which is Half Duplex operation, also included are the timings. If you wish to speed up the polling times you may choose to set the modems timing parameters to the shorter time periods, all modems in the system must be set the same way. A word of caution, speeding things up can introduce errors into the system, especially if there is noise present. OFF ON RTS-CTS SOFT CAR ECHO------FULL Duplex REC SQLCH CAR DET ANTI-STR 12ms 10ms 6ms 8ms 6ms 5ms 3ms 4ms FULL DUPLEX HALF DUPLEX HALF DUPLEX 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 10

12 Full Duplex Operation (4 Wire 2pairs ) TMC Host RS232 4xx 4xx 4xx 4-WIRE FULL DUPLEX systems use 2 pairs of wire to interconnect the Master and Slave Controllers. One pair carries data from the Master to the Local Controllers and the second pair carries data back from the Local Controllers to the Master. The far end modem does not have to wait till the master has completed its message before it starts to respond, therefore faster turn around times can be achieved. Audio Out from the Master connects to the Local Controllers AUDIO. Audio In at the Master connects to all of the Local Controllers AUDIO. The DIP Switch diagram below is where the adjustments are made to operate in the 4 wire mode, note also you can change various timing parameters. The settings shown are for 4 Wire which is Full Duplex operation, also included are the timings. If you wish to speed up the polling times you may choose to set the modems timing parameters to the shorter time periods, all modems in the system must be set the same way. A word of caution, speeding things up can introduce errors into the system, especially if there is noise present. OFF ON RTS-CTS SOFT CAR ECHO------FULL Duplex REC SQLCH CAR DET ANTI-STR 12ms 10ms 6ms 8ms 6ms 5ms 3ms 4ms FULL DUPLEX HALF DUPLEX HALF DUPLEX 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 11

13 HOW TO ADD FIBER AND RADIO S TO YOUR SYSTEM At a location where you want to connect to a Fiber or Spread Spectrum Radio you can either add a Stand Alone version of the Plug-in, or simply remove the plug-in and install an external Stand Alone with its main port cabled to the communications port on the controller. However which method you choose, the Stand Alone must be equipped with an optional Key On Data (KOD) Module. Stand Alone Model with the Optional Key On Data Module. On the Stand Alone model an Optional KOD module can be installed. This module is designed to create RTS Handshaking to control the transmit phase of the modem. The Handshake is only created when data flows in or out of the modems data port, the direction is user defined. A practical use of this feature is when you want to connect to a DCE device such as a radio into a 2/4Wire FSK system heading back to the TMC. The problem here is the radio has no means to raise and lower RTS to turn the modems FSK transmitter on or off. We cannot wire RTS high (+5V) as this would permanently turn the FSK transmitter on and block all other modem communications on the cable pair. The solution is to install a KOD module. Internal KOD RS232 Data Port RTS 2/4 Wire FSK FSK Section (M odem ) DATA KOD M odule RS232 DATA TXD RXD With a KOD device installed, data flowing from the radio arrives at the KOD module which in turn raises RTS to the modems input. RTS (raised) now keys the modem on and data is then transmitted. At the end of the data transmission, the KOD device lowers RTS which turns off the modems transmitter (carrier). Now the transmitter is quiet which allows another modem on the line to transmit. Remember all modems share the same cable pair so every modem has to take its turn to broadcast back the TMC (Poll Response). External KOD RS232 Data Port TXD 2/4 Wire FSK FSK Section (M odem ) DATA KOD M odule RTS KOD RTS DB9 Pin 1 RJ45 Pin 2 RXD DATA The KOD s direction can be reversed so that the modem can generate RTS (KOD) and handshake any attached DCE device. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 12

14 KOD APPLICATIONS City Hall RS Series Plug-in Housed in a R Rack at City Hall Radio Radio Receive Pair RXD 2 TXD 3 S.GND 5 2 or 4 Wire Application 4xxSA TXD RXD S.GND Aux Port KOD Main Port Local Controller # 1 KOD Direction Switched to Internal 3 TXD 2 RXD 5 S.GND 8 RTS 400SA 1 DCD 4Wire 4 Wire 4Wire 4xx Plug-in No KOD Required Local Controller # Series 4Wire City Hall Receive Pair. Polled Response Flow Diagram From Controllers # xx Radio Flow Diagram Radio Data FSK TXD RXD KOD Switched to Internal S.GND 400SA 2Wire Controller # 1 Data Local Controller 4xx Plug-in Controller # 2 Controller # 2 Controller # 3 Keyed On Data, Shared Path The above applications show how to attach generic products to the GDI 4xx Series of s with the KOD option installed. Note: No KOD option is required for the modem if you use GDI Radios and Fiber Digital s as these products are designed to plug and play together. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 13

15 More Applications City Hall RS232 Plug-in Housed in a R Rack at City Hall 4xx Series 2 or 4 Wire to Fiber to Radio GDI s = Maximum Capabilities 4xxSA KOD Switched to Internal Aux Port Main Port 2 RXD 3 TXD 5 S.GND Local Controller Note: FDM s can be switched to operate in any mode such as: 2 TXD 6 3 RXD 5 S.GND 4 Main Port RTS CTS Optional A Daisy Chain as shown, or Single Fiber Ring or Dual Counter Rotating Ring (Self Healing) GDI FDM2SA Fiber Digital Aux Port GDI FDM2SA Fiber Optic GDI FDM2SA Fiber Optic 2 TXD 6 3 RXD 5 5 S.GND 4 Main Port GDI SS Radio Aux Port 2 or 4 Wire to Fiber Generic s = Basic Capability 4xxSA KOD Switched to Internal Aux Port Main Port 3 TXD 2 RXD 5 S.GND Generic SS Radio 2 or 4 Wire TXD 6 RXD 5 S.GND 4 Generic Fiber Optic Generic Fiber Optic Generic Fiber Optic 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 14

16 Repeater Applications Using a Pair of Stand Alone s Communications Flow Communications Flow FSK Data Data FSK Data X Repeater Cable # IFC-A01160 To City Hall TMC 4 Wire 2 Wire 4xxSA Auxiliary Port 4 S. GND 6 TXD 5 RXD 2 CD 8 RTS S. GND 4 RXD 5 TXD 6 RTS 8 CD 2 Auxiliary Port 4xxSA 2 Wire Down Stream 4 Wire Main Port Main Port RS232 Local Controller When there is little or no signal left and you still need to go that last mile you can add an additional modem to form a back to back repeater. It is important to place the repeater at a point where the signal is still good as it s better to regenerate signals from a clean reliable point than a noisy one, this may be 2 or 3 modems back from the end failure point. The incoming and out going cable pair(s) need to be separated, one modem connects to the incoming cable while the other connects to the out going cable, then connect the two modems together via Auxiliary Data Ports. The Local Controller connects to the modems Main Data Port on the TMC (City Hall) side. The incoming FSK tones are demodulated to RS232 signals and then passed to the second modem where they are modulated back to FSK tones. This process is generally referred to as repeating the signal when in actuality we have regenerated clean FSK signals from the digital input. Basically we have isolated one side of the cable system from the other and start all over with clean regenerated signals. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 15

17 A Word on Dynamic Range All Model 4xx series modems have 42db of dynamic range based on a 0dBm transmit level into a 600 Ohm load. How far will the signal go? This is a not an easy one to answer and can only be generalized as many factures come into play such as; 1. Condition of the cable, water penetration, corrosion etc. 2. The wire gauge, larger is better. 3. The number of modems attached to the cable pair, as you add more modems the resulting load impedance presented to the transmitting source will decrease across the cable pair. This will cause the signal level to decrease to a point where there is insufficient signal level over induced noise to operate error free, thus limiting the transmission distance. 4. Cross talk from adjacent pairs, due to high levels or a short between adjacent pairs. 5. Induced noise due to poor grounding of the cable/cabinet. 6. Baud Rates, as the frequency goes up the transmission distance decreases, 1200 baud may go 20 miles while baud on the same cable pair will typically be less than 10 miles. Pushing the Envelope (Making the Last Mile) Additional distance can sometimes be obtained by boosting the gain of the last modem on the line; this is achieved through a DIP switch and only affects this modem. This external DIP switch, marked Load Compensation, is located on the switch bank on the underside of the modem. Selecting HI will increase the gain of the modem and may give you that extra signal level to make that last mile. For normal operation leave the switch set to 600 ohms. Before installing any modem make sure that the cable pairs have Lightning Protectors installed at each modem location, please make sure that the protective device is grounded according to National Electrical Code. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 16

18 Notes: Contents of this user guide may not be copied or published without the written consent of GDI Communications LLC, Verdi, Nevada. The contents of this user guide are deemed to be correct at the time of publishing and are offered as a guide only; GDI Communications LLC is not liable for any inaccuracies or omissions. 4xx Plug-in Preliminary Generic User Guide. 20 Jan 06 17

19 Contents of this user guide may not be copied or published without the written consent of GDI Communications LLC, Verdi, Nevada. The contents of this user guide are deemed to be correct at the time of publishing and are offered as a guide only; GDI Communications LLC is not liable for any inaccuracies or omissions.