Omega OMEGABUS A2400 User Manual Download Page 62

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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.

Summary of Contents for OMEGABUS A2400

Page 1: ...omega com e mail info omega com For latest product manuals omegamanual info User sGuide A2400 Series Radio Modem Module Shop online at MADE IN...

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Page 3: ...beaccurate however noresponsibilityisassumedfor possible inaccuracies or omissions Applications information in this manual is intended as suggestions for possible use of the products and not as explic...

Page 4: ...85 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...

Page 5: ...dio Modem Interface Module A2400 fills the need for a low cost intelligent interface between the radio modem and the RS 485 data acquisition devices In a typical system as shown in Figure 1 1 there is...

Page 6: ...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...

Page 7: ...wer 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 th...

Page 8: ...parity etc The memory is nonvolatile which means that the information is retained even if power is removed No batteries are used so it is never necessary to open the module case The EEPROM provides t...

Page 9: ...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 t...

Page 10: ...ssor The RS 232 port connects to a second UART external to the microprocessor All data communicated to and from the A2400 on either port must pass through the microprocessor The micro controls the dat...

Page 11: ...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...

Page 12: ...e If the CTS line is not used it may be left open and delay time T2 will function as a software handshake 5 DO0 ARTS This is a digital output that can be configured to perform two functions The functi...

Page 13: ...ar end of the RS 485 bus The 1 K ohm resistors are used to bias the signal lines to a Mark condition This is necessary when all transmitters of the RS 485 bus are off which is the most prevalent condi...

Page 14: ...flush characters until another valid prompt is found If 32 characters are received after a prompt without a carriage return found the data is considered to be noisy and the character filter is reset f...

Page 15: ...on 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 t...

Page 16: ...nd is ready for data This signal may be connected to the CTS input of the A2400 to provide hardware handshaking The delay period T2 ends when either the CTS signal is detected or the T2 timer ends whi...

Page 17: ...les is performed with two or three character ASCII command codes such as RD for Read Data A complete description of all commands is given in the Chapter 4 A typical command response sequence would loo...

Page 18: ...is similar to RS 422 in that it uses a balanced differential pair of wires switching from 0 to 5V to communicate data RS 485 receivers can handle common mode voltages from 7V to 12V without loss of da...

Page 19: ...Communication 3 3...

Page 20: ...ransmission line should be avoided For wire runs greater than 500 feet total the end of the bus should be terminated with a 220 resistor connected between DATA and DATA The A2400 has a resistor built...

Page 21: ...common mode voltage For reliable operation the common mode voltage should be kept below 5V To avoid problems with voltage drops modules may be powered locally rather than transmitting the power from t...

Page 22: ...r sign character is used to generate a short response message from the module A short response is the minimum amount of data necessary to complete the command The second prompt character is the pound...

Page 23: ...the address character the module will ignore any character below ASCII 23 except of course CR This allows the use of spaces ASCII 20 within the command message for better readability if desired The l...

Page 24: ...sage times listed in Table 2 0 to calculate the maximum time necessary to respond to a command Long Form Responses When the pound sign command prompt is used the module will respond with a long form r...

Page 25: ...orted For example Command 1WE no checksum Response Command 1WEF0 with checksum Response Command 1WEF1 incorrect checksum Response 1 BAD CHECKSUM Command 1WEF one extra character Response 1 SYNTAX ERRO...

Page 26: ...ger The variables must be converted to like types in the host software to determine equivalency If checksums do not agree a communications error has occurred If a module is setup to provide linefeeds...

Page 27: ...Prompt 1RLP 7D RS Read Setup 1RS 31070000 RSP Read Short Prompt 1RSP 7B RSU Read Setup 1RSU 31070000 RT1 Read Time delay 1 1RT1 00100 00 RT2 Read Time delay 2 1RT2 00352 00 RT3 Read Time delay 3 1RT3...

Page 28: ...controls digital output DO0 ARTS pin on the module connector The digital output allows the module to control an external circuit under host command The DO command requires an argument of two hex char...

Page 29: ...digital output There is no software provision to read the state of the digital output Extended Address EA The Extended Address EA command allows the user to set the two byte address to be used with E...

Page 30: ...mmand 1ID TANK FARM 1 Response 1ID TANK FARM 1CD Long Prompt LP The Long Prompt command allows the user to specify a desired long prompt ASCII character A two character hexadecimal value is used to de...

Page 31: ...t transmits either a valid long form or short form prompt the open channel will close Read Data RD TheReadData RD commandisusedtoreadanalogdatafromanaloginput products The RD command is included in th...

Page 32: ...Response 1RID TANK FARM 11F Read Long Prompt RLP The Read Long Prompt command reads back the extended addressing long form command prompt stored in the module s nonvolatile memory with the Long Prompt...

Page 33: ...setup message When reading the setup message with a checksum be sure not to confuse the checksum with the setup information Command 1RS Response 31050000 Command 1RSU Response 31050000 Command 1RS Res...

Page 34: ...esponse 00050 00 Command 1RT3 Response 1RT3 00050 00E2 SetUp Command SU Each module contains an EEPROM which is used to store module setup information such as address baud rate parity etc The EEPROM i...

Page 35: ...ve decimal digits decimal point and two more digits Command 1T1 00100 00 Set T1 to 100 ms Response Command 1T1 00100 00 Set T1 to 100 ms Response 1T1 00100 008A Set Time Delay 2 T2 The time delay T2 i...

Page 36: ...itted data and the turn off of the radio transmitter and it allows the host to poll more data without keying the transmitter on and off During time T3 the host may transmit another command which would...

Page 37: ...prompts will cause an error when opening a channel in Extended Addressing mode Command 1SP40 40 Response Command 1SP40 Response 1SP4062 Write Enable WE The Write Enable WE command must precede comman...

Page 38: ...ge begins with a different character Host computer software can identify an error by the first character it is not necessary to read the whole string ADDRESS ERROR There are six ASCII values that are...

Page 39: ...ity type does not match the module parity In this situation the easiest solution may be to change the host parity to obtain communications At this point the parity in the module may be changed to the...

Page 40: ...ries to replace TheEEPROMhasmanyadvantagesoverDIPswitchesorjumpersnormally used for option selection The module never has to be opened because all of the options are selected through the communication...

Page 41: ...changing communications parameters address baud rate parity which will result in a loss of communications between the host and the module In some cases the user may have to resort to using Default Mod...

Page 42: ...d that only ASCII codes for printable characters be used 21 to 7E which greatly simplifies system debugging with a dumb terminal Refer to Appendix A for a list of ASCII codes Table 5 1 lists the print...

Page 43: ...by the module Bit 5 turns the parity on and off If bit 5 is 0 the parity of the command string is ignored and the parity bit of characters transmitted by the module is set to 0 If bit 5 is 1 the pari...

Page 44: ...m the Read Setup command with this module we would get Command 1RS Response 31070000 Let s say we wish to change the baud rate to 9600 baud The code for 9600 baud is 0010 from Table 5 2 This would cha...

Page 45: ...ponds The last resort is to set the module to Default Mode where the baud rate is always 300 Setting a string of RS 232C modules to a new baud rate requires special consideration Refer to Chapter 3 fo...

Page 46: ...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 extended addressing...

Page 47: ...ong enough to ensure that the transmitter is on The delay times are specified using commands from the A2400 command set and are stored in nonvolatile memory The A2400 uses three programmable delay tim...

Page 48: ...nicating 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...

Page 49: ...nsmit line When the transmit data is complete the A2400 starts delay time T3 After the completion of delay time T3 the A2400 turns off the RTS signal and is now ready for the next command response seq...

Page 50: ...ion 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...

Page 51: ...me a maximum of 5 watts and this figure should be used in determining the power supply current requirement In some cases the A2400 may be operated by stealing power from a host computer or terminal Ma...

Page 52: ...als should idle at 10Vdc 4 If you are using a serial communications converter A1000 ensure that the communications Baud Rate switch is set to the proper Baud Rate value 5 Confirm software communicatio...

Page 53: ...mal command structure address space is limited to 122 points Extended addressing allows an addressing range of more than 1 8 million points More realistically if only printable characters are used for...

Page 54: ...Extended Addressing 9 2 Figure 7 1 Typical system overview...

Page 55: ...e to the modules in a normal fashion Command 1RD Response 00100 00 typical Command 2RD Response 00123 45 typical Note that A2400 address 02 is still in a Close Channel state No data received by this A...

Page 56: ...ilar to the normal protocol The Extended Address commands are initiated with a character left curly brace ASCII 7B or a character right curly brace ASCII 7E The prompt is analogous to the prompt in th...

Page 57: ...eguard against the possibility of two or more A2400 s being on at the same time which could result in data collisions This is done automatically whether the A2400 is addressed or not No response is ge...

Page 58: ...and Command 01 1RD Response 00100 00 In this command form the 01 is an implied Open Channel command to A2400 01 The is also an implied Close Channel command to all other A2400 s It is followed immedia...

Page 59: ...at channel 01 has been closed The same level of confirmation can be used with the Open Channel command Command 02OC Response Command 02OC Response 02OC1E 1E is the checksum The explicit forms of the O...

Page 60: ...lid address and a valid command This simple command response protocol must be strictly observed to avoid communi cations collisions and data errors In the transparent mode the module acts like an open...

Page 61: ...communications 2 10 bit data format 3 The equipment must work on a command and response protocol and that protocol must not interfere with valid D series prompts or the customer programmed prompt of a...

Page 62: ...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...

Page 63: ...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...

Page 64: ...Transparent Mode 10 5 Example 4 A2400 interfacing several instruments with a string of modules...

Page 65: ...Transparent Mode 10 6 Figure 10 5 Adding secondary control using A2400 modules...

Page 66: ...be enabled while the module is operating in either the normal or the extended addressing mode The TRANSPARENT mode has to be set up manually or with the utility software Command 1RS Response 31070000...

Page 67: ...otherwise shall not exceed the purchase price of the component upon which liability is based In no event shall OMEGA be liable for consequential incidental or special damages CONDITIONS Equipment sold...

Page 68: ...rs Turbine Paddlewheel Systems Totalizers Batch Controllers pH CONDUCTIVITY pH Electrodes Testers Accessories Benchtop Laboratory Meters Controllers Calibrators Simulators Pumps Industrial pH Conducti...

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