RCP TTY Site Settings for Dual System

The dual-system setups are in the site custom section of the RCP8 non-volatile setups. You can access these from a setup terminal or from IRIS systems through the awtx program from an X terminal.

  1. Use Dual/Redundant system configuration: YES

    Answer YES to enable dual-system support.

    Answer NO to disable dual-system support.

    note If you answer NO to this question, the safety features that prevent simultaneous usage of the 2 RCP8s are not in effect. Vaisala does not recommend that you answer NO for a dual-system.
  2. This RCP8 is the ’A’ unit: NO

    The 2 RCP8s are named the A and B units.

    tip To avoid confusion, Vaisala recommends that you put physical A and B labels on the 2 units.

    If you do not want to use the A and B labels, use this question to declare the single-letter identifier that appears in the TB title bar for each unit.

    Note that if you use the TB (title bar) option for the first line of the RCP8 front panel display (configured in the site display section), then the characters [A] or [B] appear on the top line of the RCP8 front panel to reflect your choice.

  3. Identifying letter for this unit: ’A’

    Respond YES for your A unit and then for the B unit setups respond NO.

  4. Default powerup operating mode: Auto

    You may choose the initial power up mode (None/A/B/Auto) of a dual RCP8 system. On power up, RCP8 first waits for guidance, either from IRIS or from the other RCP8, about which mode to enter. If the other RCP8 is dead, and if no mode requests have come in from IRIS, then the unit switches to its default powerup mode. Otherwise, the unit acquires the mode of the other RCP8, or follows the direction of IRIS.

    Selecting the AUTO initial powerup mode handles the case of starting an active scan with no user intervention when just one RCP8 is first switched on. Without this, the user would first have to explicitly choose AUTO from an IRIS Dual Switching Menu. But sometimes this is what you want; and by selecting the powerup mode of None, the system remains in maintenance mode until IRIS user makes a specific choice.

  5. This RCP8 is the ’Preferred’ unit: NO

    The Preferred unit value resolves negotiation “ties” by the switching algorithm. When confronted with a choice of using the A or B unit, and all else is equal, the Preferred unit is used. Vaisala recommends that you make system A the preferred unit:

    • In the system A setup, respond YES
    • In the system B setup, respond NO
  6. Include Data Processor NST faults: NO

    This question allows you to include the fault status of the Data Processor reported by IRIS when determining whether a given channel is okay.

    • Answering YES means that both the data processor and the radar workstation must be working in order for the channel to be considered okay.
    • Answering NO causes only the radar server computer to be checked.
  7. Cooldown time after becoming inactive: 3.0 sec
  8. Additional warmup time when switching: 3.0 sec

    For redundant switching of antenna control, a minimum of 2 seconds is required by RCP8 itself. The value that is used depends on the specific characteristics of the system and should be measured for each system.

  9. Allow voluntary flipping between units: NO

    The Dual/Redundant system code can switch between systems in response to requests from the host computer. RCV05 and XMT05 serial formats include 2 bits to control these transitions. One bit (WouldUse) announces that the host computer would like to use the antenna (whether or not it is available). The other bit (Relinquish) indicates that control can be voluntarily relinquished to the other system.

    When RCP8 receives a Relinquish offer, it checks the other unit to verify that it:

    • Communicates properly
    • Does not indicate any faults
    • Has WouldUse TRUE and Relinquish FALSE

    Under these conditions, if control were offered to the other unit, it would actually be in a position to accept it; and so, the switch-over is made at that instant. Since the algorithm only flips to a system that is actually ready to go, it automatically optimizes scheduling of the antenna as each radar is able to use it.

    The additional logic variables, cDrcpWouldUse, cDrcpRelinquish, cDrcpDisabled, cDrcpWarmup, cDrcpOkay, cDrcpMaint, sOtherDrcpWouldUse, sOtherDrcpRelinquish, sOtherDrcpAlive, sOtherDrcpDisabled, sOtherDrcpWarmup, sOtherDrcpActive, and sOtherDrcpOkay, appear in the control logic editor when voluntary flipping is enabled.

    The next group of questions concerns how IRIS Mode (as defined in the Radar Status Menu) is forced by RCP8 when an RCP8 switches from INACTIVE to ACTIVE state and vice versa.

    The first set of questions is for the switch from INACTIVE to ACTIVE. The example responses are for a redundant system with the modes configured as described in Configuring IRIS for Dual-System Support:

    Choose: None Fixed Inherit Resume 
Mode switch strategy when ACTIVE: Inherit 
    IRIS mode #1 is valid to request: NO 
    IRIS mode #2 is valid to request: NO 
    IRIS mode #3 is valid to request: YES 
    IRIS mode #4 is valid to request: YES 
    IRIS mode #5 is valid to request: NO 
    IRIS mode #6 is valid to request: NO 
    IRIS mode #7 is valid to request: NO 
Default mode to resolve illegal requests:3

    The 2 RCP8s negotiate which is the active system such that only one system can be ACTIVE at any given time. (Note that both systems could be INACTIVE). When a system is switched into active mode, it commands its IRIS to change operating modes (that is, the Radar Status Menu mode is loaded per RCP8 command). This question is used to determine what IRIS mode is commanded when a system is switched to active. RCP8 calls IRIS modes 1-7. The relation to IRIS mode names is made in IRIS Setups (RCP section). See Configuring IRIS for Dual-System Support. The strategy choices are:

    Fixed
    RCP forces IRIS into a particular operating mode.
    None
    In this case RCP does not request any IRIS modes.
    Inherit
    RCP switches IRIS into the operating mode that was being used before the switch. If you respond Inherit, you are prompted to say what modes are valid to inherit.
    Resume
    RCP switches IRIS to the mode that RCP was last run in. This is useful in the case of dual frequency systems that are sharing an antenna system since it allows a system to resume operation in passive mode even if it is not the active controller. It is not used for redundant systems.

    Here the recommended response for a redundant system is Inherit so that when a system becomes active, it continues operation in whatever mode the other RCP had been using. This assures that if a system is running and faults, it continues in the same mode of operation after an automatic switch.

    In the case of Inherit or Resume, RCP8 prompts you to specify which modes of operation are valid to inherit (or resume) when the system becomes active. In this case, based on the example IRIS mode configuration in Configuring IRIS for Dual-System Support, the AIRPORT and AERIAL modes would be allowed.

    The final question in this sequence above specifies the mode to use when the inherited mode does not match any of the allowed modes. For example, if both systems are in STANDBY when a switch is made, the new ACTIVE system tries to inherit the STANDBY mode (mode 2 in our example). This is not a valid active mode so the ACTIVE system would start mode 3 (AIRPORT) instead.

  10. Allow mode changes within IRIS: YES
    Responding NO prevents both automatic and manual IRIS mode changes (from IRIS Radar Status Menu). RCP8 continually forces IRIS mode.

    The second set of questions is for the switch from ACTIVE to INACTIVE.

    Choose: None Fixed Inherit Resume 
Mode switch strategy when INACTIVE: 
FIXED Fixed IRIS mode to request: 2 
    Allow mode changes within IRIS: NO

    Fixed is recommended for redundant systems, since it can be used to force IRIS into a STANDBY mode when its RCP8 becomes inactive. In this example, mode Z is used, which corresponds to the mode called STANDBY.

    Mode to request during Maintenance ACTIVE: 0 
Mode to request during Maintenance INACTIVE: 1 
    Allow mode changes from within IRIS: YES

    In the example, the STANDBY mode is forced when the system goes INACTIVE. Note that this makes it impossible to do any modification of IRIS mode for development or maintenance. In this case, it is recommended that you temporarily respond YES to this question.

    These questions specify what IRIS modes should be set when RCP8 is intentionally disabled (placed in “Maintenance Mode”) by either the hardware A/B switch or the Select switch in IRIS Switching menu.

    You may choose IRIS mode to request for Maint Active and for Maint Inactive. If the requested mode is nonzero, then an additional question appears to choose whether auto mode switching is allowed. A recommended strategy is to request a mode of zero in Maint Active, so that a running RCP continues doing whatever it was doing already. Maint Inactive should request IRIS maintenance RST mode, and allow auto switching.