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MADE IN
User’s Guide
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A2400 Series
Radio Modem Module
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A2400 USERS MANUAL REVISED: 4/17/95 OMEGA ENGINEERING ONE OMEGA DRIVE P. O. BOX 4047 STAMFORD, CT 06907 PHONE: 1-800-DAS-IEEE FAX: 203-359-7990 e-mail: das@omega.com www.omega.com The information in this publication has been carefully checked and is believed to be accurate; however, no responsibility is assumed for possible inaccuracies or omissions. Applications information in this manual is intended as suggestions for possible use of the products and not as explicit performance in a specific a
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TABLE OF CONTENTS CHAPTER 1 Getting Started Quick Hook-Up 1-3 Default Mode 1-4 CHAPTER 2 Functional Description Block Diagram 2-1 CHAPTER 3 Communications RS-485 3-2 Multi-party Connection 3-3 RS-485 Multidrop System 3-4 CHAPTER 4 Command Set Table of Commands 4-6 User Commands 4-6 Error Messages 4-13 CHAPTER 5 Setup Information and Command Command Syntax 5-1 Setup Hints 5-8 CHAPTER 6 Delay Time Programming CHAPTER 7 Power Supply CHAPTER 8 Troubleshooting CHAPTER 9 Extended Addressing CHAPTER 10
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Chapter 1 Getting Started Introduction This manual describes the function and application of the Radio Modem Interface Module (A2400). The A2400 provides an intelligent interface between radio modems available from many manufacturers and devices designed to operate on a bi-directional RS-485 serial bus. Although the A2400 has been designed specifically for our family of industrial I/O modules, it may also be used with other RS-485 devices. Figure 1.1 depicts a typical application that incorporat
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Getting Started 1-2 A2400 is to control the slave transmitter to allow multiple slave sites. Figure 1.1 System Overview. Leased Lines This manual has been written with emphasis on radio modems. However, the A2400’s may be used just as effectively with leased telephone lines. Typically, leased lines do not have dial-up capability and some means of addressing and multiplexing must be employed if multiple stations are used. A2400’s may be used with leased line modems in an identical manner as with
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Getting Started 1-3 Getting Started To get your A2400 up and running for an initial check-out, connect the unit to a power supply and terminal as shown in Figure 1.2. The power supply can be any dc source from 10 to 30 volts, capable of 1 Watt of power. The terminal can be any RS-232 dumb terminal set for 300 baud. A computer configured as a terminal can also be used. Be sure to ground the DEFAULT* pin. Figure 1.2 A2400 Quick Hookup. After checking the connections, power up the A2400. Type the f
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Getting Started 1-4 This message is terminated with a carriage return. If the response message cannot be obtained, re-check all the wiring, making sure that the proper power is on the A2400 connector and that the DEFAULT* line is shorted to the GND pin. The terminal must be set to 300 baud. If, after several attempts, the response message does not appear, refer to Chapter 8 Troubleshooting in this manual. If you have an IBM PC or compatible computer, running the S1000 setup software will ease th
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Getting Started 1-5 values (NULL, CR, $, #, {, }). A dummy address must be included in every command for proper responses. Setup information in an A2400 may be changed at will with the SetUp (SU) command. Baud rates and parity setups may be changed without affecting the Default values of 300 baud and no parity. When the DEFAULT* pin is released, the module automatically performs a program reset and configures itself to the baud rate and parity stored in the setup information. The Default Mode is
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Chapter 2 Functional Description Block Diagram The A2400 is an RS-232/RS-485 converter specifically designed to inter- face D series RS-485 modules to radio modems. To this end the A2400 provides three functions: 1) Perform the RS-232 to RS-485 electrical conversion. 2) Control the data direction of the RS-485 bus. 3) Create hand-shaking signals to control the modem. A simplified block diagram of the A2400 is illustrated in Figure 2.1. This shows the RS-485 and RS-
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Functional Description 2-2 DEFAULT +5V RTS CTS RX RX TX TX UART MICRO- PRCESSOR +5 5.6K EEPROM DO0/RTS Figure 2.1 A2400 Block Diagram.
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Functional Description 2-3 Pinout 1) TRANSMIT This is the RS-232 Transmit output from the A2400. This pin is normally connected to the Receive input of a modem. This output is also used to connect to a terminal or computer to configure the A2400 2) RECEIVE This is the RS-232 Receive input of the A2400. This pin is normally connected to the Data Output of a radio modem. This input is also used to connect to a terminal or computer to configure the A2400 3) RTS RS-232 Request To Send output. This
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Functional Description 2-4 bus. This bus connects to multidrop RS-485 devices such as D series modules. 8) (G)DATA- This is the negative polarity of the differential RS-485 bus. 9) (R)V+ A2400 power connection. The A2400 operates on 10 to 30 volts dc. 10) (B)GND This is the ground connection common to all circuits. The A2400 does not have isolation between power and the two communications ports. Note that pins 7 through 10 are designated Y, G, R, and B respectively. This corresponds to the Yell
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Functional Description 2-5 reaching the RS-485 bus. The first operation performed on the modem data is to check for noise and framing errors. If either condition exists, the bad character is re-formatted as a null character (ASCII $00). Since the null is not a legal character for use as an address in the modules, transmitting a null is preferable to aborting the character when an error is detected. This cuts down on the possibility of a module being incorrectly addressed. After noise and framin
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Functional Description 2-6 addressed command and it responds back with information on the bus. The A2400 receives this information and places it in a buffer that can hold up to 96 characters. The parity of received characters is ignored. As soon as a character is received, the A2400 starts a timing sequence to control the modem transmitter. Three user-programmable timers, T1, T2, and T3 control the data flow. See Figure 2.2 . Figure 2.2 Programmable Delay Times.
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Functional Description 2-7 T1 As soon as the A2400 detects a character in the RS-485 receive buffer, time delay T1 is activated. This is a dead time to allow the host to prepare for the receipt of a message. This is particularly important when a simplex connec- tion is used, where the send and receive data is transmitted on the same frequency. During this time the A2400 creates no control output, but any data received on the RS-485 port is stored in the receive buffer. At the end of time T1, th
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Chapter 3 Communications Introduction The A2400 modules have been carefully designed to be easy to interface to all radio modems and many leased-line modems. All communications to and from the modules are performed with printable ASCII characters. This allows the information to be processed with string functions common to most high- level languages such as BASIC. The ASCII format makes system debugging easy with a dumb terminal. This system allows multiple modules to be connected through the A24
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Communication 3-2 improper command prompt or address is transmitted. The table below lists the timeout specification for each command assuming that delay times T1, T2, T3 = 0: Table 3.1 Response Timeout Specifications. Mnemonic Timeout DO, OC, CC, RD, REA, RID, RLP, RS, RSP, RSU, ≤ 10 ms RT1, RT2, RT3, WE EA, ID, LP, RID, RR, SP, SU, T1, T2, T3 ≤ 100 ms The timeout specification is the turn-around time from the receipt of a command to when the module starts to transmit a response. Data Format A
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Communication 3-3
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Communication 3-4 RS-485 Multidrop System Figure 3.1 illustrates the wiring required for multiple-module RS-485 system. Notice that every module has a direct connection to the A2400. Any number of modules may be unplugged without affecting the remaining modules. Each module must be setup with a unique address and the addresses can be in any order. All RS-485 modules must be setup for no echo to avoid bus conflicts (see Setup). Also note that the connector pins on each module are labelled with n
