F280X

FOM II Series

RS-232 / MIL-STD-188C

Fiber Optic Modem

Technical Manual

See Technical Data Sheet

See Unusual RS232 Application

Download Manual PDF

www.versitron.com

May 2001

Copyright May 2001

VERSITRON, Inc.

83 Albe Drive / Suite C

Newark, DE 19702

PROPRIETARY DATA

All data in this manual is proprietary and may not be disclosed,

used or duplicated, for procurement or manufacturing purposes,

without prior written permission by

VERSITRON, Inc .

WARRANTY

1. You call VERSITRON at (302) 894-0699 or (800) 537-2296 and obtain a Return Maintenance Authorization (RMA) Number. Please reference your RMA number on the outside of the shipping box.

2. Shipping charges are pre-paid.

No other warranty is expressed or implied and we are not liable for consequential damages. For repairs outside of the warranty period, the same procedure must be followed.

TABLE OF CONTENTS

SECTION 1: DESCRIPTION OF EQUIPMENT

1.1 INTRODUCTION

1.2 DESCRIPTION OF EQUIPMENT

1.2.1 Functional Characteristics

1.2.2 Physical Characteristics

1.3 SPECIFICATIONS

SECTION 2: INSTALLATION

2.1 GENERAL

2.2 SITE SELECTION AND MOUNTING

2.3 POWER REQUIREMENTS

2.3.1 Installation with AC Power

2.3.2 Installation with DC Power

2.4 SWITCH SETTINGS

2.5 TIMING MODE

2.5.1 Source Timing

2.5.2 Terminal Timing

2.5.3 Internal Timing

2.6 LOOPBACK

2.6.1 Fiber / Copper Loopback

2.6.2 Remote / Local Loopback

2.7 INITIAL CHECKOUT PROCEDURE

SECTION 3: OPERATION

3.1 INTRODUCTION

3.2 STATUS INDICATORS / AUDIBLE ALARMS

3.3 Operating Controls

SECTION 4: THEORY OF OPERATION

4.1 INTRODUCTION

SECTION 5: MAINTENANCE AND TROUBLESHOOTING

5.1 INTRODUCTION

5.2 FAULT ISOLATION

List of ILLUSTRATIONS

1. OVERALL VIEW, F280x MODEM

2. CIRCUIT CARD LAYOUT, F280X MODEM

3. INTERFACE EXTENDER CONFIGURATION

4. MODEM LINK CONFIGURATION

5. DC POWER SUPPLY CONNECTIONS

6. SWITCH SETTINGS

7. INTERNAL TIMING MODES

List of TABLES

1. ENCLOSURES / CHASSIS

2. SW3 SETTINGS FOR INTERNAL TIMING

3. BASIC SWITCH SETTINGS

4. NON-OPERATIONAL INDICATORS

SECTION 1

DESCRIPTION OF EQUIPMENT

1.1 INTRODUCTION

This manual provides general and detailed information on the installation and operation of the Model F280X FOM II Series RS-232 Fiber Optic Modem. Section 1 contains a general description of the equipment. Section 2 contains installation instructions. Section 3 contains operating instructions. Section 4 provides the theory of operation. Section 5 contains maintenance and troubleshooting information. Figure 1 is an overall view of the F280X.

1.2 DESCRIPTION OF EQUIPMENT

Functional Characteristics

Model F280X are fiber optic products designed for use as a RS-232 interface extender (see Figure 2) or a modem link (see Figure 3). These units are DTE/DCE switch selectable and interface with other F280X Modems in VERSITRON'S FOM II series. F280X Modems use multimode fiber optic cable up to 2 Km (6,560 ft.) for 850nm multimode optics, 8 Km (26,240 ft.) for 1300nm multimode optics, and single mode fiber optic cable up to 14 Km (45,920 ft.) for 1300nm single mode optics. F280X Modems have a maximum data rate of 76.8 Kbps and appear fully transparent in both directions. The unit can generate 18 internal clock frequencies. F280X Modems fully support the interface control signals associated with the EIA RS-232 and MIL-STD-188C standards. This is accomplished by multiplexing the control signals along with clock and data signals and transmitting this serialized signal to the remote unit. At the remote unit the signal is demultiplexed and applied to the interface.

1.2.2 Physical Characteristics

F280X Modems measure 7.0" wide x 0.84" high x 11.6" deep and are designed to be mounted in VERSITRON HF series enclosures or chassis (Ref. Table 1 for dimensions). Standalone options include single- (HF-1) and dual-card (HF-2) enclosures. Rack mount options include 2-slot side-by-side (HF-2SS) and 20-slot (HF-20) chassis. For HF-1, HF-2, or HF-2SS installations, each F280X Modem requires a power adapter. The adapter plugs into a one-pin connector on the back of the card to provide power. A female DB25 connector provides the interface and two ST connectors provide the fiber optic interface. Both connectors are located on the back of the card. When using the HF-20 chassis, VERSITRON AC150W power supply / system monitors are used to provide power to the chassis. One AC150W utilizes two slots in the HF-20. Two AC150W units are recommended for power redundancy. F280X Modems have seven indicators: power (PWR), alarm (ALM), transmit data (TXD), receive data (RXD), transmit clock (TXC), receive clock (RXC), and Loopback (LOOP).

FIGURE 1. OVERALL VIEW, F280X MODEM

FIGURE 2. CIRCUIT CARD LAYOUT, F280X MODEM

*¹ Note: One Power Adapter per Modem required.

TABLE 1. ENCLOSURES / CHASSIS

FIGURE 3. INTERFACE EXTENDER CONFIGURATION

FIGURE 4. MODEM LINK CONFIGURATION

1.3 SPECIFICATIONS

Data Rate: Continuously variable from 0 Bps to 76.8 Kbps synchronous (source or terminal timing), asynchronous, or isochronous (Clock must be supplied externally). DTE source timing applications above 56 Kbps may be dependent upon cable length. Consult factory to discuss your specific application and configuration requirements.

Operating Mode/Range: Simplex, Half or Full duplex. Maximum operating range is 2 Km (6,560 ft.) with 850nm multimode optics or 8 Km (26,240 ft.) with 1300nm multimode optics on multimode fiber optic cable, and 14 Km (45,920 ft.) with 1300nm single mode optics on single mode fiber optic cable.

Optical Interface: ST connectors, compatible with 50/125, 62.5/125 or 100/140 µm multimode fiber optic cable for 850nm or 1300nm multimode operation, or 8/125, 9/125, or 10/125 µm single mode fiber optic cable for 1300nm single mode operation.

Digital Interface: Signal levels and format conform to EIA RS-232, RS-423 or MIL-STD-188C. The F280X has a female DB25 connector for connecting to a terminal, with a gender changer required for connecting to a modem. The unit is switch selectable between DCE/DTE operation.

Sample Rate: Control signals are sampled at an 18.75 KHz rate. If an asynchronous data signal is used instead of a control signal the sample rate will result in 5% distortion at 1 Kbps. Data and clock signals are sampled at 300 KHz.

Dimensions: 7.0" (17.8 cm) W x 0.84" (2.1 cm) H x 11.6" (29.5 cm) D.

Weight: 16.0 oz. (0.45 kg).

Power Requirements: VAC source with AC-to-DC power adapter (VERSITRON Model PSAC08 US, PSAC09 EUR) providing 12 VDC, 1A; or + 12 VDC source.

Environment: 0° to +50°C (32° to +122°F) operating temperature; up to 95% relative humidity (non-condensing); up to 10,000 feet altitude; storage temperature -40° to +70° C.

*Note: Multimode tests were performed on 62.5/125 µM multimode fiber optic cable.

Single Mode tests were performed on 9/125 µM single mode fiber optic cable.

SECTION 2

INSTALLATION

2.1 GENERAL

This section contains information on the installation and initial checkout of the F280X Modems. Section 2.2 contains general information on site selection and mounting. Section 2.3 describes power requirements. Section 2.4 describes switch settings. Section 2.5 describes timing modes. Section 2.6 describes loopback features. Section 2.7 contains initial checkout procedures.

2.2 SITE SELECTION AND MOUNTING

F280X Modems are designed to connect to the serial port (DB25 Connector) of terminal equipment with a customer supplied cable. F280X Modems are designed to be installed in either VERSITRON HF-1 or HF-2 standalone enclosures, or to be rack mounted in a VERSITRON HF-2SS or HF-20 19-inch standard chassis (Ref. Table 1 for enclosure and chassis dimensions). When installed in a HF-1, HF-2, or HF-2SS, space for the power adapter must also be provided.

2.3 POWER REQUIREMENTS

F280X Modems are designed to operate from an AC power adapter or a +12 VDC power source.

2.3.1 Installation with AC Power

Before inserting the VERSITRON power adapter, PSAC08 (US) or PSAC09 (EUR), into an AC power source, the plug should be connected to the Modem. There are no special tools required.

2.3.2 Installation with DC Power

DC power may be used instead of a power adapter. This requires a 2.5 mm socket, J3 (location shown in figure 1.5) with the positive voltage on the center and the common on the concentric supplying 12VDC at 1A as shown below:

FIGURE 5. DC POWER SUPPLY CONNECTIONS

2.4 SWITCH SETTINGS

There are a number of switches on the circuit card of the F280X Modem, used to select between DTE/DCE operation, internal/external clock selection, the internal clock data rate, and several loopback functions. Figure 4 shows the physical location of all of the switches, labeled SW1 through SW11. With the exception of the loopback switch (SW1), which is on the front panel of the Modem card, all of the switches should be set to the desired position prior to applying power to the Modem, and then left in those positions unless the overall link characteristics change.

Switch 3 (SW3), located between the optical modules and the XILINX field programmable gate array (FPGA) chip, contains 8 ON-OFF switch positions. The first 3 positions determine the expected interface standard input. Since the complete family of F28XX Series Modems includes products that operate per the RS-530 standard, there are switch positions for settings that are not applicable to the Model F280X Modems, as they operate only with RS-232 standard inputs. For the same reason, there is no Switch 2 (SW2) on a F280X Modem. For SW3, Position 2 is set to ON for DCE operation, OFF for DTE operation. Position 1 must remain ON. SW3, Position 3 changes the interface from 0° phase inversion (RS-232 standard, SW3, Position 3 OFF) to 180° phase inversion (MIL-STD-188C, SW3, Position 3 ON). Positions 4 through 8 of SW3 are used to set the clock rate for internal-timing operation. There are 18 different clock rates that may be chosen by the settings of SW3 (Ref. Table 2).

FIGURE 6. SWITCH SETTINGS

TABLE 2. SW3 SETTINGS FOR INTERNAL TIMING

TABLE 3. F280X SWITCH SETTINGS

2.5 TIMING MODE

F280X Modems can operate in three different timing modes: Source Timing, Terminal Timing, and Internal Timing. All timing modes are application specific and can be configured using Switch 4, Position 1 as listed in Table 3. As shown in Figure 4, Switch 4 (SW4), located to the left of the FPGA, also contains 8 ON-OFF switch positions. Positions 4 through 8 are not used for the F280X Modems and should be left in the OFF position. The following sections describe the operation and associated required switch settings for each mode.

2.5.1 Source Timing

A realignment circuit is needed in the Source (external) Timing configuration to account for the inherent delays and jitter introduced by noise and asynchronous sampling at all frequencies. The realignment circuit is only used on the DTE units. A clock detection circuit checks for a clock signal on input pin 15 of the DB25 interface. If there is no clock signal on pin 15, no realignment takes place and data is output from the unit as it was received from the fiber optic input. If there is a clock signal present, the realignment circuit processes the data signal recovered from the fiber optic receiver before it is output onto pin 2. In Source Timing mode, the F280X Modems support transmitted and received data, transmitted and received clocks, and eight control signals. The unit shall transmit and receive signals at a data rate between 50 Bps and 76.8 Kbps with a bit error rate of 1x10^-9. Switch 4, Position 2 should be OFF for source timing.

2.5.2 Terminal Timing

The Terminal (external) Timing mode is the basic mode of operation for the F280X Modems. There is no circuit needed for data realignment. In Terminal Timing mode, the F280X Modems support transmitted and received data, transmitted and received clocks, and eight control signals. Data signals at a data rate from 50 Bps to 76.8 Kbps are processed transparently by the Modem, with a bit error rate of 1x10 ^-9 . Switch 4, Position 2 should be ON for terminal timing.

2.5.3 Internal Timing

F280X Modems can supply clock frequencies internally while configured as a DCE. SW3, Positions 4 through 8 allow the user to select 18 different clock frequencies (Ref. Table 2). The internal timing mode is set by turning SW4, Position 1 ON. When SW4, Position 1 is in the ON position, the board is configured as a null modem. In this configuration, the terminal timing (TT) clock signal on input pin 24 of the DB25 interface and the transmit clock signal (TXC), input on pin 15 of a DTE unit, are disconnected and replaced with the internally generated clock. In a null modem configuration, the internal clock is used throughout the circuit. In the interface extender configuration, the internal clock generated by the DCE Modem is output on pin 24 of the DTE Modem. Both configurations are illustrated in Figure 6. When SW4, Position 1 is in the OFF position the internal clock is off.

F igure 7. INTERNAL TIMING MODES

2.6 LOOPBACK

F280X Modems have two loopback features. The first loopback feature allows the user to test the fiber optic circuitry of the unit, the fiber optic circuitry of the unit at the receiving end, the copper circuitry of the unit, and the copper circuitry of the unit at the receiving end. The second loopback feature loops the control signals RTS and CTS.

2.6.1 Fiber / Copper Loopback

This loopback feature of the F280X Modems allow the user to test the fiber optic circuitry of the unit and the fiber optic circuitry of the unit at the receiving end. The fiber optic input and outputs are connected to a multiplexer. The multiplexer is controlled by the front-panel switch (SW1). When SW1 is ON, the multiplexer control bit goes high, the fiber optic input data is looped to the fiber optic output and sent back to the source. The copper signal enters the board through the interface circuitry to the multiplexer circuit. The signals get multiplexed, demultiplexed and transmitted back to their source. This is true for all data, clock, and control signals. If the fiber optic output and input signals match, and the copper signals match, the optical and interface circuits of both units are working properly. When SW1 is OFF, the multiplexer control bit goes low, and the unit functions normally.

2.6.2 Remote / Local Loopback

The Remote / Local Switch, SW4, Position 3, is used to loop control signals RTS and CTS. This is to accommodate equipment that lacks the ability to respond to an RTS signal. When SW4, Position 3 is ON, a CTS input signal is connected to RTS output and an RTS input is connected to CTS output. When SW4, Position 3 is OFF, CTS-IN is connected to CTS-OUT and RTS-OUT is connected to RTS-IN (Ref. Table 3).

2.7 INITIAL CHECKOUT PROCEDURE

F280X Modems contain no power on/off switch. Once the unit is properly installed and power is applied it may be considered fully operational. The power indicator should remain on as long as power is supplied to the unit

Before beginning system operation the following items should be checked to verify proper installation:

1. Verify that the power plug is seated fully into the Modem or the Modem is seated firmly in the rack mount enclosure.

2. Verify that the fiber optic cable is crossed transmit to receive from unit one to unit two.

3. Verify that the alarm LED goes out when the signal is applied to the optical receiver of the F280X.

4. Verify the switch settings for the circuit configuration (i.e. internal/external timing).

If a malfunction is detected during the initial checkout procedure, refer to Chapter 5 for information on isolating the malfunction in the unit.

SECTION 3

OPERATION

3.1 INTRODUCTION

This chapter contains a description of the operating controls and indicators associated with the F280X Modems. Since the F280X Modems are designed for continuous and uninterrupted operation, there are no operating requirements. Once the F280X Modem is powered up it should remain in service as long as required.

3.2 STATUS INDICATORS/AUDIBLE ALARM

There are 7 indicators on the F280X Modem: power (PWR), alarm (ALM), transmit data (TXD), receive data (RXD), transmit clock (TXC), receive clock (RXC), and Loopback (LOOP). No audible alarm is available.

3.3 Operating Controls

The only operating controls associated with the F280X Modems are those used to select between DTE/DCE, internal clock selection, or remote/local (CTS/RTS loop) (Ref. Figure 5). This selection is normally done at the time of installation. Further changes are not required unless the system requirements change.

SECTION 4

THEORY OF OPERATION

4.1 INTRODUCTION

Basic operation of F280X Modems is similar to a four-channel, full duplex multiplexer. The first channel is used for data. The next two channels are used for transmit and receive clock, while the fourth multiplexer channel is used for aggregated control signals. This technique provides full transparency for the link, even when both clocks originate at the Modem. The F280X Modem supplies both transmit and receive clocks which are transmitted through the link and applied directly to the terminal.

The interface control signals are processed in a similar manner. The Request to Send signal from the terminal is transmitted through the link and applied to the Modem. When the Modem responds with Clear to Send, it will be transmitted through the link and applied to the terminal. With this technique, the terminal will see the RTS/CTS delay established by the Modem. The unit is also capable of looping RTS/CTS for interface equipment that does not support control signals.

If a fully transparent synchronous link is not required, the clock and control paths may be used as additional asynchronous data paths. The transmit and receive clock inputs will handle data rates from 0 to 76.8 Kbps asynchronously; the control paths will handle data rates up to 1 Kbps with 5% distortion.

SECTION 5

MAINTENANCE AND TROUBLESHOOTING

5.1 INTRODUCTION

This chapter contains general information designed to isolate a malfunction in the F280X Modem to a replaceable unit. These units are not equipped with redundancy. Therefore, a failure in one of these units would interrupt service.

5.2 FAULT ISOLATION

The steps in Table 4 should be taken to check a non-operating Modem.