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| int SM_ReadHoldingRegisters |
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SM_HANDLE |
handle, |
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int |
start, |
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int |
number, |
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unsigned char * |
values | |
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Reads a 16-bit value from the Sealevel I/O device, depending on the model.
- Deprecated:
- Version 3.0.4 - Version 5.0
- Parameters:
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| [in] | handle | Valid handle returned by SM_Open(). |
| [in] | start | Modbus address to begin the read (zero-indexed). |
| [in] | number | Quantity of holding registers to read. |
| [out] | values | Register state values. |
- Return values:
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| >=0 | Number of bytes successfully returned in result array. |
| -1 | Invalid SeaMAX handle. |
| -2 | Connection is not established. Check the provided Connection object state. |
| -3 | Read error waiting for response. Unkown Modbus exception. |
| -4 | Illegal Modbus Function (Modbus Exception 0x01). |
| -5 | Illegal Data Address (Modbus Exception 0x02). |
| -6 | Illegal Data Value (Modbus Exception 0x03). |
| -7 | Modbus CRC was invalid. Possible communications problem. |
This function performs different tasks depending on the model of Sealevel I/O device. For more information, see
- Note:
- Modbus holding registers are 16-bit wide registers. Therefore, each read will result in 2 bytes in the result array. For multi-register reads, the high-order byte will reside in the first byte (result[0]) with the lower-order byte residing thereafter (result[1]). Other register bytes subsequently follow the same pattern.
- Warning:
- The result array parameter should have enough allocated space, before calling this method, to hold 2 bytes for every register requested.
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