Omega A2400 manual

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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 omission[...]

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[...]

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 specific[...]

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 o[...]

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 termi[...]

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[...]

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, t[...]

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[...]

Functional Description 2-2 EEPROM MICRO- PRCESSOR +5 5.6K DO0/RTS RX TX CTS RTS +5V UART RX TX DEFAULT Figure 2.1 A2400 Block Diagram.[...]

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 Out[...]

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[...]

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 t[...]

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 u[...]

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. Duri[...]

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[...]

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 ?[...]

Communication 3-3[...]

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. [...]

Communication 3-5 becomes an important consideration. The GND wire is used both as a power connection and the common reference for the transmission line receivers in the modules. Voltage drops in the GND leads appear as a common-mode voltage to the receivers. The receivers are rated for a maximum of -7V. of common-mode voltage. For reliable operati[...]

Chapter 4 A2400 Command Set The A2400 operates with a simple command/response protocol to control all module functions. A command must be transmitted to the A2400 by the host computer or terminal before the A2400 will respond with useful data. A module can never initiate a communications sequence. A list of available commands and a sample format fo[...]

Command Set 4-2 All commands must be terminated by a carriage return character (ASCII $0D). In all command examples in this text the carriage return is either implied or denoted by the symbol ‘CR’. Data Structure Many commands require additional data values to complete the command definition as shown in the example commands in Table 4.1. The pa[...]

Command Set 4-3 A command/response sequence is not complete until a valid response is received. The host may not initiate a new command until the response from a previous command is complete. Failure to observe this rule will result in communications collisions. A valid response can be in one of three forms: 1) a normal response indicated by a ‘ [...]

Command Set 4-4 interprets a command, it looks for the two extra characters and assumes that it is a checksum. If the checksum is not present, the module will perform the command normally. If the two extra characters are present, the module will calculate the checksum for the message. If the calculated checksum does not agree with the transmitted c[...]

Command Set 4-5 Example: Append a checksum to the command $1WE Characters: $ 1 W E ASCII hex values: 24 31 57 45 Sum (hex addition) 24 + 31 + 57 + 45 = F1 The checksum is F1 (hex). Append the characters F and 1 to the end of the message: $1WEF1 Example: Verify the checksum of a module response *1WEF7 The checksum is the two characters preceding the[...]

Command Set 4-6 Each A2400 user command is described in detail following Table 4.1. All of the commands are listed in alphabetical order according to command nomenclature. Table 4.1 A2400 Command Set Command and Definition Typical Typical Command Response Message Message ($ prompt) DO Digital Output $1DO01 * RD Read Data $1RD *+99999.99 REA Read Ex[...]

Command Set 4-7 Command Descriptions All the commands may be used with normal addressing or Extended Addressing unless otherwise noted. Commands that are exclusive to the Extended Address mode are noted near the right hand margin. For example: Closed Channel (CC) (Extended) Closed Channel (CC) (Extended) The Close Channel (CC) command is an Extende[...]

Command Set 4-8 To turn the output off you could use the command: Command: $1DO00 Response: * Command: #1DO00 Response: *1DO004E Digital output 0 shares the connector pin with the Alternate RTS. Bit 3 of byte 4 of the SetUp command is used to configure this pin as either digital output or RTS function. See chapter 5 for details. The digital output [...]

Command Set 4-9 Identification (ID) The IDentification command allows the user to write a message into the nonvolatile memory which may be read back at a later time with the Read IDentification (RID) command. It serves only as a convenience to the user and has no affect on the module operation. Any message up to 16 characters long may be stored in [...]

Command Set 4-10 Open Channel (OC) (Extended) The Open Channel (CC) command is used to open the communications data channel in Extended Address mode. The open channel will allow serial communications data to flow from the A2400’s RS-232 port to a string of RS- 485 devices. The open communications channel will remain open until a Close Channel (CC[...]

Command Set 4-11 In this example the ‘30’ and ‘31’ are the hex ASCII codes for the characters ‘0’ and ‘1’ respectively. The Extended Address is ‘01’. Read Identification (RID) The Read IDentification command reads back the user data stored by the IDentification (ID) command. The ID and RID commands are provided as a convenience [...]

Command Set 4-12 Command: #1RR Response: *1RRFF Read Setup (RS or RSU) The read setup command reads back the setup information stored in the A2400’s EEPROM with the SetUp (SU) command. The response to the RS or RSU command is four bytes of information formatted as eight hex characters. The response contains the module’s channel address, baud ra[...]

Command Set 4-13 Read Time Delay 1 (RT1) The Read Time 1 command reads back the time value stored in EEPROM by T1 command. Command: $1RT1 Response: *+00100.00 Command: #1RT1 Response: *1RT1+00100.00DC Read Time Delay 2 (RT2) The Read Time 2 command reads back the time value stored in EEPROM by the T2 command. Command: $1RT2 Response: *+00500.00 Com[...]

Command Set 4-14 The SetUp command requires an argument of eight hexadecimal digits to describe four bytes of setup information. Command: $1SU31070007 Response: * Command: #1SU31070007 Response: *1SU3107000795 Set Time Delay 1 (T1) T1 is a programmable time delay used to control the RTS output. T1 is used to guarantee a dead time between the comple[...]

Command Set 4-15 T2 is specified in units of milliseconds with a range of 0 to 2000ms. The time data must be formatted as a plus sign, five decimal digits, a decimal point, and two additional digits: Command: $1T2+00350.00 (Set T2 to 350 ms.) Response: * Command: #1T2+00350.00 (Set T2 to 350 ms.) Response: *1T2+00350.0092 Set Time Delay 3 (T3) T3 i[...]

Command Set 4-16 Short Prompt (SP) The Short Prompt command allows the user to specify a desired short prompt ASCII character. A two character hexadecimal value is used to define the desired ASCII character prompt. Note: Short Prompt command may be sent to the module in either normal addressing or Extended Addressing mode. The user-defined short fo[...]

Command Set 4-17 Command: }01WE Response: *01WE27 If a module is write enabled and the execution of a command results in an error message other than WRITE PROTECTED, the module will remain write enabled until a command is successfully completed resulting in an ‘*’ prompt. This allows the user to correct the command error without having to execu[...]

Command Set 4-18 COMMAND ERROR This error occurs when a command is not recognized by the module. Often this error results when a command is sent with lowercase letters. All valid commands use uppercase characters. PARITY ERROR A parity error can only occur if the module is setup with parity on. Usually a parity error results from a bit error caused[...]

Chapter 5 Setup Information/SetUp Command The A2400 features a wide choice of user configurable options which gives them the flexibility to operate on virtually any radio or leased-line modem. The user options include a choice of baud rate, parity, address, and many other parameters. The particular choice of options for a module is referred to as t[...]

SetUp Command 5-2 A typical SetUp command would look like: $1SU31070102 Notice that each byte is represented by its two-character ASCII equivalent. In this example, byte 1 is described by the ASCII characters ‘31’ which is the equivalent of binary 0011 0001 (31 hex). The operand of a SU command must contain exactly 8 hex (0-F) characters. Any d[...]

SetUp Command 5-3 to communicate with a module with an unknown address is with the Default Mode. The most significant bit of byte 1 (bit 7) must be set to ‘0’. In addition, there are six ASCII codes that are illegal for use as an address. These codes are $00, $0D, $24, $23, $7B, $7D which are ASCII codes for the characters NUL, CR, $, #, {, and[...]

SetUp Command 5-4 Byte 2 Byte 2 is used to configure some of the characteristics of the communica- tions channel; linefeeds, parity, and baud rate. Linefeeds The most significant bit of byte 2 (bit 7) controls linefeed generation by the module. This option can be useful when using the module with a dumb terminal. All responses from the modules are [...]

SetUp Command 5-5 changed, a module reset must occur. A reset is performed by sending a Remote Reset (RR) command or powering down. This extra level of write protection is necessary to ensure that communications to the module is not accidentally lost. This is very important when changing the baud rate of an RS-232C string. For more information on c[...]

SetUp Command 5-6 Command: $1RR Response: * Up to this point all communications have been sent at 300 baud. The module will not respond to any further communications at 300 baud because it is now running at 9600 baud. At this point the host computer or terminal must be set to 9600 baud to continue operation. If the module does not respond to the ne[...]

SetUp Command 5-7 Byte 3 This byte contains determines which addressing mode will be used. The default value for this byte is ‘00’. Normal addressing The normal addressing mode refers to the D series protocol of using a single ASCII character for a channel address. There are up to 124 possible addresses in this mode. Extended addressing The ext[...]

Chapter 6 Delay Time Programming Each A2400 contains user-programmable delays to properly sequence the transmission of data from a remote radio modem to a host computer. The delays are required to sequence an external transmit enable signal required by most radio modems. The external transmit enable signal most often used is the RS-232 Request to S[...]

Delay Time Programming 6-2 Figure 6.1 Programmable delay times. As described in figure 6.1 the communications sequence assumes a host computer communicating with a module on the RS-485 bus through the A2400. In an idle condition, when no data is present on the communications lines, the A2400 turns its RS-485 transceiver to receive mode and monitors[...]

Delay Time Programming 6-3 the data over the RS-485 bus. This data is normally command data being sent to a module on the bus. When the RS-232 command data is complete, the A2400 immediately turns its RS-485 transceiver back to receive mode and monitors the RS-485 bus. In normal operation the A2400 looks for a D series response prompt character, ei[...]

Delay Time Programming 6-4 Command: $1T3+00050.00 (set T3 to 50 ms.) Response: * Time may be set to 1 ms. resolution. The T1, T2, T3 commands are write-protected and must be preceded by a Write Enable (WE) command. The delay times are stored in nonvolatile memory. The delay times are inactive in Default Mode. The delay times stored in the A2400 may[...]

Chapter 7 Power Supply A2400 modules may be powered with an unregulated +10 to +30Vdc. Power-supply ripple must be limited to 5V peak-to-peak, and the instanta- neous ripple voltage must be maintained between the 10 and 30 volt limits at all times. All power supply specifications are referred to the module connector; the effects of line voltage dro[...]

Chapter 8 Troubleshooting Symptom: RS-232 Module is not responding to commands 1 Using a voltmeter, measure the power supply voltage at the +Vs and GND terminals to verify the power supply voltage is between +10 and +30Vdc. 2 Verify using an ohmmeter that there are no breaks in the communica- tions data lines. 3 Connect the module to the host compu[...]

Chapter 9 Extended Addressing The A2400 may be configured to a special command format called Extended Addressing. This mode uses a different prompt, either ‘{‘ or ‘}’ to distinguish it from the regular command syntax. The major difference in syntax for the Extended Addressing mode is that it uses a two-character address. A typical command i[...]

Extended Addressing 9-2 Figure 7.1 Typical system overview.[...]

Extended Addressing 9-3 When the system is initially powered up, the A2400’s are set to the Close Channel condition. This means that no data received by the radio modems will pass to the RS-485 bus at either site. In order to communicate to the modules, one of the A2400’s must be set to the Open Channel condition: Command: {01OC Response: * Thi[...]

Extended Addressing 9-4 Figure 7.1 shows a very simple system but the same addressing methodmay be used to construct very large systems. Each RS-485 string may handle up to 122 addresses, and up to 14884 A2400’s may have unique addresses. Structured Addressing Even for a relatively small system, it can be advantageous to employ a hierarchical add[...]

Extended Addressing 9-5 All commands that are available with single-byte addressing may be accessed with Extended Addressing, and vice-versa; the only exceptions being the OC and CC commands, which can be used only with Extended Addressing. OC and CC Command Formats Once an A2400 has been configured correctly in Extended Address mode, the only comm[...]

Extended Addressing 9-6 This command will close the channel at A2400 #01 and open the channel at A2400 #02. This is the quickest method of opening and closing A2400 channels. It also offers the least amount of data security. A2400 #01 was closed solely upon detecting the ‘{‘ character. There is no confirmation that A2400 #01 is closed. If A2400[...]

Extended Addressing 9-7 To explicitly close the channel of A2400 #01: Command: {01CC Response: * The response message is a confirmation that the channel has been closed. A higher level of confirmation can be obtained with the long form: Command: }01CC Response: *01CC11 (‘11’ is the checksum) The response confirms that channel ‘01’ has been [...]

Chapter 10 Transparent Mode The A2400 is an RS-232/RS-485 converter designed to provide interface virtually any product to a radio and leased telephone line modems. In normal operation the A2400 is configured to work on the D series protocol, but it may be configured to a special communications mode called the transparent mode. When used in the tra[...]

Transparent Mode 10-2 The following examples 1 through 4 illustrate the application of the A2400 in the extended mode of operation. The A2400 in transparent mode allows equipment from various sources to be added to a network of D series modules. However the following rules must apply: 1. half duplex communications. 2. 10-bit data format. 3. The equ[...]

Transparent Mode 10-3 Example 2. A2400 networking several RS-232 devices to a host com- puter. Figure 10.2 A2400 networking several RS-232 devices to a host computer.[...]

Transparent Mode 10-4 Example 3. A2400 interfacing a device with a string of modules. Figure 10.3 A2400 interfacing a laboratory instrument with modules.[...]

Transparent Mode 10-5 Example 4. A2400 interfacing several instruments with a string of modules.[...]

Transparent Mode 10-6 Figure 10.5 Adding secondary control using A2400 modules.[...]

Transparent Mode 10-7 Figure 10.5 shows an application where the user was able to add a back-up or secondary control supervision using the A2400 modules. The original installation of the flow computers and PLC’s were controlled by the control station using Modbus protocol with RS-485. The user was able to use A2400 modules on the RS232 ports of t[...]

WARRANTY / DISCLAIMER OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a period of 13 months from date of purchase. OMEGA’s WARRANTY adds an additional one (1) month grace period to the normal one (1) year product warranty to cover handling and shipping time. This ensures that OMEGA’s customers r[...]

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