In particular, constants are defined for Modbus function codes and * error codes, and static methods are provided to convert these constants * to descriptive strings. */ public class Modbus { private Modbus () {} /** * Official maximum number of bytes in a "Protocol Data Unit". * The PDU includes the function code and following fields (but * excludes any CRC/LRC). */ public static final int MAX_PDU_SIZE = 253; /** * Implementation limit on number of bytes in a "Protocol Data Unit" * (i.e. determined by buffer sizes). * The PDU includes the function code and following fields (but * excludes any CRC/LRC). *
The value 65534 is actually the largest PDU that can be carried by the * TCP packet type. */ public static final int MAX_IMP_PDU_SIZE = 65534; /** * Minimum sensible value for maximum PDU size. */ public static final int MIN_PDU_SIZE = 20; /** * Official maximum number of data bytes that can be read in a single * request (using functions 1, 2, 3, 4). *
This is currently 250 bytes, which is equivalent to 125 registers * or 2000 coils/discrete-inputs. *
Functions 1,2,3,4 responses have an overhead of 2 bytes, so the maximum * of data bytes would give a PDU size of 250 + 2 = 252 bytes, which is * 1 less than the maximumu PDU size (253 bytes). */ public static final int MAX_READ_BYTES = 250; /** * Official maximum number of data bytes that can be written in a single * request (using functions 15, 16). *
This is currently 246 bytes, which is equivalent to 123 registers * or 1968 coils/discrete-inputs. *
Function 15 and 16 requests have an overhead of 6 bytes, so the maximum * of data bytes would give a PDU size of 246 + 6 = 252 bytes, which is * 1 less than the maximumu PDU size (253 bytes). */ public static final int MAX_WRITE_BYTES = 246; /** Function code. */ public static final int FUNC_READ_COILS = 1; /** Function code. */ public static final int FUNC_READ_DISCRETE_INPUTS = 2; /** Function code. */ public static final int FUNC_READ_HOLDING_REGISTERS = 3; /** Function code. */ public static final int FUNC_READ_INPUT_REGISTERS = 4; /** Function code. */ public static final int FUNC_WRITE_SINGLE_COIL = 5; /** Function code. */ public static final int FUNC_WRITE_SINGLE_REGISTER = 6; /** Function code. */ public static final int FUNC_READ_EXCEPTION_STATUS = 7; /** Function code. */ public static final int FUNC_DIAGNOSTICS = 8; /** Function code. */ public static final int FUNC_GET_COMM_EVENT_COUNTER = 11; /** Function code. */ public static final int FUNC_GET_COMM_EVENT_LOG = 12; /** Function code. */ public static final int FUNC_WRITE_MULTIPLE_COILS = 15; /** Function code. */ public static final int FUNC_WRITE_MULTIPLE_REGISTERS = 16; /** Function code. */ public static final int FUNC_REPORT_SLAVE_ID = 17; /** Function code. */ public static final int FUNC_READ_FILE_RECORD = 20; /** Function code. */ public static final int FUNC_WRITE_FILE_RECORD = 21; /** Function code. */ public static final int FUNC_MASK_WRITE_REGISTER = 22; /** Function code. */ public static final int FUNC_READ_WRITE_MULTIPLE_REGISTERS = 23; /** Function code. */ public static final int FUNC_READ_FIFO_QUEUE = 24; /** Function code. */ public static final int FUNC_ENCAPSULATED_INTERFACE_TRANSPORT = 43; /** Function code. */ public static final int FUNC_MONITOR_INPUT_REGISTERS = 65; /** Function code. */ public static final int FUNC_MONITOR_DISCRETE_INPUTS = 66; /** Function code. */ public static final int FUNC_MONITOR_HOLDING_REGISTERS = 67; /** Function code. */ public static final int FUNC_MONITOR_COILS = 68; /** Function code. */ public static final int FUNC_MONITOR_FILE_RECORDS = 69; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_QUERY_DATA = 0; /** Diagnostic sub-function code. */ public static final int DIAG_RESTART_COMM_OPTION = 1; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_DIAGNOSTIC_REGISTER = 2; /** Diagnostic sub-function code. */ public static final int DIAG_CHANGE_ASCII_INPUT_DELIMITER = 3; /** Diagnostic sub-function code. */ public static final int DIAG_FORCE_LISTEN_ONLY_MODE = 4; /** Diagnostic sub-function code. */ public static final int DIAG_CLEAR_COUNTERS = 10; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_BUS_MESSAGE_COUNT = 11; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_BUS_COMM_ERROR_COUNT = 12; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_BUS_EXCEPTION_COUNT = 13; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_SLAVE_MESSAGE_COUNT = 14; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_SLAVE_NO_RESPONSE_COUNT = 15; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_SLAVE_NAK_COUNT = 16; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_SLAVE_BUSY_COUNT = 17; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_BUS_CHARACTER_OVERRUN_COUNT = 18; /** Diagnostic sub-function code. */ public static final int DIAG_RETURN_OVERRUN_ERROR_COUNT = 19; /** Diagnostic sub-function code. */ public static final int DIAG_CLEAR_OVERRUN_COUNTER = 20; /** Diagnostic sub-function code. */ public static final int DIAG_GET_CLEAR_MODBUS_PLUS_STATISTICS = 21; public static final int COMM_EVENT_RCV_OK = 0x80; public static final int COMM_EVENT_RCV_COMM_ERROR = 0x80|0x02; public static final int COMM_EVENT_RCV_OVERRUN = 0x80|0x10; public static final int COMM_EVENT_RCV_LISTEN_ONLY = 0x80|0x20; public static final int COMM_EVENT_RCV_BROADCAST = 0x80|0x40; public static final int COMM_EVENT_SND_OK = 0x40; public static final int COMM_EVENT_SND_EXCEPTION = 0x40|0x01; public static final int COMM_EVENT_SND_ABORT = 0x40|0x02; public static final int COMM_EVENT_SND_BUSY = 0x40|0x04; public static final int COMM_EVENT_SND_NAK = 0x40|0x08; public static final int COMM_EVENT_SND_TIMEOUT = 0x40|0x08; public static final int COMM_EVENT_SND_LISTEN_ONLY = 0x40|0x08; public static final int COMM_EVENT_LISTEN_ONLY = 0x04; public static final int COMM_EVENT_RESTART = 0x00; /** Exception code. */ public static final int ERROR_NONE = 0; /** Exception code. */ public static final int ERROR_ILLEGAL_FUNCTION = 1; /** Exception code. */ public static final int ERROR_ILLEGAL_DATA_ADDRESS = 2; /** Exception code. */ public static final int ERROR_ILLEGAL_DATA_VALUE = 3; /** Exception code. */ public static final int ERROR_SERVER_FAILURE = 4; /** Exception code. */ public static final int ERROR_ACKNOWLEDGE = 5; /** Exception code. */ public static final int ERROR_SERVER_BUSY = 6; /** Exception code. */ public static final int ERROR_MEMORY_PARITY = 8; /** Exception code. */ public static final int ERROR_PATH_UNAVAILABLE = 0x0a; /** Exception code. */ public static final int ERROR_TIMED_OUT = 0x0b; /** Device Identification Object Id */ public static final int DEVICE_VENDOR_NAME = 0x00; /** Device Identification Object Id */ public static final int DEVICE_PRODUCT_CODE = 0x01; /** Device Identification Object Id */ public static final int DEVICE_MAJOR_MINOR_REVISION = 0x02; /** Device Identification Object Id */ public static final int DEVICE_VENDOR_URL = 0x03; /** Device Identification Object Id */ public static final int DEVICE_PRODUCT_NAME = 0x04; /** Device Identification Object Id */ public static final int DEVICE_MODEL_NAME = 0x05; /** Device Identification Object Id */ public static final int DEVICE_USER_APPLICATION_NAME = 0x06; /** Device Identification Object Id */ public static final int DEVICE_MIN_RESERVED = 0x07; /** Device Identification Object Id */ public static final int DEVICE_MAX_RESERVED = 0x7f; /** Device Identification Object Id */ public static final int DEVICE_MIN_PRIVATE = 0x80; /** Device Identification Object Id */ public static final int DEVICE_MAX_PRIVATE = 0xff; /** Encapsulated Interface (MEI) Transport types */ public static final int MEI_CANOPEN = 0x0d; public static final int MEI_READ_DEVICE_IDENTIFICATION = 0x0e; /** * Returns string describing Modbus function code * @param code the function code * @return descriptive string, or null if non-standard function */ public static String getFunctionName (int code) { String str; switch (code & 0x7f) { default: str = null; break; case FUNC_READ_COILS: str = "Read Coils"; break; case FUNC_READ_DISCRETE_INPUTS: str = "Read Discrete Inputs"; break; case FUNC_READ_HOLDING_REGISTERS: str = "Read Holding Registers"; break; case FUNC_READ_INPUT_REGISTERS: str = "Read Input Registers"; break; case FUNC_WRITE_SINGLE_COIL: str = "Write Single Coil"; break; case FUNC_WRITE_SINGLE_REGISTER: str = "Write Single Register"; break; case FUNC_WRITE_MULTIPLE_COILS: str = "Write Multiple Coils"; break; case FUNC_WRITE_MULTIPLE_REGISTERS: str = "Write Multiple Registers"; break; case FUNC_READ_FILE_RECORD: str = "Read File Record"; break; case FUNC_WRITE_FILE_RECORD: str = "Write File Record"; break; case FUNC_MASK_WRITE_REGISTER: str = "Mask Write Register"; break; case FUNC_READ_WRITE_MULTIPLE_REGISTERS: str = "Read/Write Multiple Registers"; break; case FUNC_ENCAPSULATED_INTERFACE_TRANSPORT: str = "MEI"; break; case FUNC_READ_EXCEPTION_STATUS: str = "Read Exception Status"; break; case FUNC_DIAGNOSTICS: str = "Diagnostics"; break; case FUNC_GET_COMM_EVENT_COUNTER: str = "Get Comm Event Counter"; break; case FUNC_GET_COMM_EVENT_LOG: str = "Get Comm Event Log"; break; case FUNC_REPORT_SLAVE_ID: str = "Report Slave ID"; break; case FUNC_READ_FIFO_QUEUE: str = "Read FIFO Queue"; break; } return str; } /** * Returns string describing Modbus diagnostics sub-function code * @param code the sub-function code * @return descriptive string, or null if non-standard sub-function */ public static String getDiagFunctionName (int code) { switch (code) { case DIAG_RETURN_QUERY_DATA: return "Return Query Data"; case DIAG_RESTART_COMM_OPTION: return "Restart Comm Option"; case DIAG_RETURN_DIAGNOSTIC_REGISTER: return "Return Diagnostic Register"; case DIAG_CHANGE_ASCII_INPUT_DELIMITER: return "Change ASCII Input Delimiter"; case DIAG_FORCE_LISTEN_ONLY_MODE: return "Force Listen Only Mode"; case DIAG_CLEAR_COUNTERS: return "Clear Counters"; case DIAG_RETURN_BUS_MESSAGE_COUNT: return "Return Bus Message Count"; case DIAG_RETURN_BUS_COMM_ERROR_COUNT: return "Return Bus Comm Error Count"; case DIAG_RETURN_BUS_EXCEPTION_COUNT: return "Return Bus Exception Count"; case DIAG_RETURN_SLAVE_MESSAGE_COUNT: return "Return Slave Message Count"; case DIAG_RETURN_SLAVE_NO_RESPONSE_COUNT: return "Return Slave No Response Count"; case DIAG_RETURN_SLAVE_NAK_COUNT: return "Return Slave NAK Count"; case DIAG_RETURN_SLAVE_BUSY_COUNT: return "Return Slave Busy Count"; case DIAG_RETURN_BUS_CHARACTER_OVERRUN_COUNT: return "Return Bus Character Overrun Count"; case DIAG_RETURN_OVERRUN_ERROR_COUNT: return "Return Overrun Error Count"; case DIAG_CLEAR_OVERRUN_COUNTER: return "Clear Overrun Counter"; case DIAG_GET_CLEAR_MODBUS_PLUS_STATISTICS: return "Get/Clear Modbus Plus Statistics"; } return null; } /** * Returns string describing Modbus Encapsulated Interface Transport * type code. * @param code the type code. * @return descriptive string, or null if non-standard type code. */ public static String getEitTypeName (int code) { switch (code) { case MEI_CANOPEN: return "CANopen General Reference"; case MEI_READ_DEVICE_IDENTIFICATION: return "Read Device Identification"; } return null; } /** * Returns error message corresponding to Modbus error code * @param code the error code * @return corresponding error message */ public static String getErrorMessage (int code) { String str; switch (code) { default: str = "Error code " + code; break; case ERROR_NONE: str = "OK"; break; case ERROR_ILLEGAL_FUNCTION: str = "Illegal function"; break; case ERROR_ILLEGAL_DATA_ADDRESS: str = "Illegal data address"; break; case ERROR_ILLEGAL_DATA_VALUE: str = "Illegal data value"; break; case ERROR_SERVER_FAILURE: str = "Server failure"; break; case ERROR_ACKNOWLEDGE: str = "Acknowledge"; break; case ERROR_SERVER_BUSY: str = "Server busy"; break; case ERROR_MEMORY_PARITY: str = "Memory parity error"; break; case ERROR_PATH_UNAVAILABLE: str = "No path available to target"; break; case ERROR_TIMED_OUT: str = "Target device failed to respond"; break; } return str; } /** Gets a help ID for the specified error code. * The help ID is "MEnn", where 'nn' is the zero-padded 2-digit * error code in decimal, or "MEXX" if the error code is invalid, * or {@code null} if the error code is ERROR_NONE. *
The help ID is intended for use in master-mode only. * Slave-mode uses a larger set of help IDs, to distinguish errors that * share the same error code. * @param code the error code. * @return the help ID for the error code. */ static String getHelpId (int code) { switch (code) { default: return "MEXX"; case ERROR_NONE: return null; case ERROR_ILLEGAL_FUNCTION: case ERROR_ILLEGAL_DATA_ADDRESS: case ERROR_ILLEGAL_DATA_VALUE: case ERROR_SERVER_FAILURE: case ERROR_ACKNOWLEDGE: case ERROR_SERVER_BUSY: case ERROR_MEMORY_PARITY: case ERROR_PATH_UNAVAILABLE: case ERROR_TIMED_OUT: return String.format ("ME%02d", code); } } /** * Throws an illegal-address Modbus exception. * @param helpId help identifier. * @param msg exception message. * @throws ModbusException */ public static void addressError (String helpId, String msg) throws ModbusException { throw new ModbusException (ERROR_ILLEGAL_DATA_ADDRESS, helpId, msg); } /** * Throws an illegal-data Modbus exception. * @param helpId help identifier. * @param msg exception message. * @throws ModbusException */ public static void dataError (String helpId, String msg) throws ModbusException { throw new ModbusException (ERROR_ILLEGAL_DATA_VALUE, helpId, msg); } }