Omega A2400 manual Chapter Delay Time Programming

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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 Send (RTS) signal.

The RS-232 RTS signal normally becomes active just before data transmis- sion begins, remains active while all data is transmitted and then is immediately turned off. This sequence is essentially the same when using radio modems. However, a certain amount of time is required after a transmit enable signal (RTS) is activated for the radio transmitter to turn on. Transmission of data cannot begin until after the transmitter is settled and ready. Since this period of time may vary from vendor to vendor, user- programmable delays are provided in the A2400. These delays can be set long 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 times to properly sequence the data applied to the radio modem. These delay times are called T1, T2, and T3.

T1 is used to allow the host transmitter to turn off. T1 may be set to guarantee a specified amount of dead time between the radio modem receive data and the leading edge of the RTS signal which is used to key the transmitter.

T2 is used to allow the radio modem transmitter time to stabilize. T2 is the time between the leading edge of the RTS signal and the beginning of data transfer.

T3 is the delay time between the last data character to be transmitted and the trailing edge of RTS which turns off the transmitter.

The three delay times each have a programmable range of 0 to 2000 ms and are specified using the standard D series data format ‘+#####.##’. The delay time values may be set to 1ms resolution. Use commands T1, T2 and T3 to specify the delay values. These commands are write protected and must be preceded by a write enable (WE) command.

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Contents User’sGuide Servicing Europe Servicing North AmericaFor immediate technical or application assistance STAMFORD, CT Phone 1-800-DAS-IEEE Revised 4/17/95Omega Engineering ONE Omega Drive BOXTable of Contents Introduction Chapter Getting StartedLeased Lines System Overview+99999.99 $1RDDefault Mode Page Chapter Functional Description Block DiagramFunctional Description Pinout Character Filter RS-485 TerminationA2400 Operation Page Programmable Delay Times Page Chapter Communications Command $1RD Response *+99999.99DO, OC, CC, RD, REA, RID, RLP, RS, RSP, RSU Communication DATA+ RS-485 Multidrop SystemPage Command Structure Chapter A2400 Command SetResponse Structure Data StructureWrite Protection Miscellaneous Protocol NotesLong Form Responses Command Checksum$1WEF ?1 Syntax Error?1 BAD Checksum A2400 User Commands RT3 A2400 Command SetClosed Channel CC Extended Command DescriptionsCommand 01CC Response Response *01CC11 Digital Output do Command $1DO01 Response Command #1DO01 Response *1DO014FExtended Address EA Command $1DO00 Response Command #1DO00 Response *1DO004E1ID Tank Farm 1CD $1ID Tank Farm#1ID Tank Farm Read Data RD Command 01OC Response Response *01OCEDOpen Channel OC Extended 1RID Tank Farm 11F $1RIDTank Farm #1RID#1RSP $1RSU#1RSU $1RSPResponse *+00100.00 Read Time Delay 1 RT1Response *1RT1+00100.00DC Read Time Delay 2 RT2 Page Page Short Prompt SP BAD Checksum Command 01WE Response *01WE27Error Messages Address ErrorValue Error Command ErrorParity Error Syntax Error$1SUbyte 1byte 2byte 3byte Chapter Setup Information/SetUp CommandCommand Syntax Byte HEX Ascii Byte 1 Ascii Printable CharactersBaud Rate ParityCommand $1RS Response *31020102 Command $1WE Command $1RS Response *31070000Command $1WE Response Command $1SU31020000 Baud Command $1RR ResponseBit Byte 2 Linefeed, Parity and Baud RateNormal addressing Chapter Delay Time Programming Delay Time Programming Page Command $1RT1 Response *+00100.00 Command $1T3+00050.00 Set T3 to 50 ms ResponseChapter Power Supply Symptom RS-485 Module is not responding to commands Chapter TroubleshootingSymptom RS-232 Module is not responding to commands Chapter Extended Addressing Command 01WE ResponseOpen/Close Channel Commands Typical system overview Command 02OC Response Command 01OC ResponseCommand $1RD Response +00100.00 Typical $2RD +00123.45 Command 01CC ResponseExtended Address Syntax Structured AddressingCommand Response OC and CC Command FormatsImplied CC Command Implied OC CommandExplicit Open and Close Channel Commands Command Response *01OC1D Single Command Module AddressCommand 01$1RD Response *+00100.00 Command 02OC Response 02OC1E ‘1E’ is the checksum Command 01CC Response 01CC11 ‘11’ is the checksumTransparent Mode Functions Chapter Transparent ModeA2400 interfacing a PLC to a leased-line modem A2400 networking several RS-232 devices to a host computer A2400 interfacing a laboratory instrument with modules Transparent Mode Adding secondary control using A2400 modules Transparent Mode WARRANTY/DISCLAIMER Shop online at omega.com