(* Paste in IMPLEMENTATION pane. This only issues FC03 reads.
   Leave run FALSE until the component is loaded and target is configured.
   Set run FALSE and allow scans to execute before stopping/downloading.
   This bench program does not implement automatic disposal on online change. *)
readDone := FALSE;
requestError := FALSE;
timeResult := SysTimeGetUs(nowUs);
IF timeResult <> 0 THEN
    RETURN;
END_IF;
nowMs := nowUs / 1000;
dataStale := NOT hasValidData;
IF hasValidData THEN
    dataStale := (nowMs - lastReadMs) > 2000;
END_IF;

pollDelay(IN := (command = 5) AND (status[1] = 3) AND (status[2] = 0),
          PT := T#200MS);

IF NOT run THEN
    IF handle <> 0 THEN
        command := 2; (* Close *)
    ELSE
        command := 0;
    END_IF;
ELSIF (handle = 0) AND (command = 0) THEN
    command := 1; (* Open *)
END_IF;

IF command = 0 THEN
    RETURN;
END_IF;

callResult := atMbCall_cext(
    command := command,
    handle := handle,
    ipAddress := ipAddress,
    port := tcpPort,
    unitId := unitId,
    functionCode := 3,
    startAddress := startAddress,
    quantity := 10,
    pData := ADR(registers[0]),
    dataCapacity := 10,
    pStatus := ADR(status[0]),
    statusCapacity := 24,
    nowMs := nowMs,
    connectTimeoutMs := 2000,
    responseTimeoutMs := 1000,
    retryDelayMs := 1000
);

IF callResult <> 0 THEN
    IF callResult = 256 THEN (* Stale handle: obtain a fresh context. *)
        handle := 0;
        command := 0;
    ELSIF (command = 6) AND ((callResult = 2) OR (callResult = 3)) THEN
        command := 5; (* Busy/offline: return to tick. *)
    ELSE
        (* Preserve callResult for diagnostics. Turning run off closes context. *)
        run := FALSE;
    END_IF;
    RETURN;
END_IF;

CASE command OF
    1: handle := status[0]; command := 9; (* Configure *)
    9: command := 3; (* Enable *)
    3: command := 5; (* Tick *)
    5:
        IF status[3] <> 0 THEN
            command := 7; (* Copy validated read result before acknowledge. *)
        ELSIF status[4] <> 0 THEN
            lastRequestResult := status[5];
            lastException := status[8];
            lastSocketError := status[7];
            requestErrorCount := requestErrorCount + 1;
            requestError := TRUE;
            command := 10;
        ELSIF (status[1] = 3) AND pollDelay.Q THEN
            command := 6; (* Submit *)
        END_IF;
    6: command := 5;
    7:
        lastReadMs := nowMs;
        hasValidData := TRUE;
        dataStale := FALSE;
        readDone := TRUE;
        successfulReadCount := successfulReadCount + 1;
        command := 10; (* Acknowledge *)
    10: command := 5;
    2: handle := 0; command := 0; hasValidData := FALSE; dataStale := TRUE;
END_CASE;