ModbusStructs.cin

Improved comments

Modbus-CAPL/include/CAPL/include/ModbusStructs.cin

@@ -1,27 +1,29 @@
 /*@!Encoding:1252*/
 variables
 {
-	// according to Modbus Specification v1.1
+	// Constant maximum values according to Modbus Specification v1.1
 	const word gMaxBitsPerRead  = 2000;
 	const word gMaxRegsPerRead  = 125;
 	const word gMaxBitsPerWrite = 1968;		// Multiple of 8!
 	const word gMaxRegsPerWrite = 123;
 
+	// Function Codes according to Modbus Specification v1.1
 	enum ModbusFuncCode
 	{
-		ReadBitsOut = 0x01,
-		ReadBitsIn = 0x02,
-		ReadRegistersOut = 0x03,
-		ReadRegistersIn = 0x04,
-		WriteBit = 0x05,
-		WriteRegister = 0x06,
-		WriteBits = 0x0F,
-		WriteRegisters = 0x10,
-		MaskRegister = 0x16,
-		ReadWriteRegisters = 0x17
+		ReadBitsOut = 0x01,					// Read  Coils
+		ReadBitsIn = 0x02,					// Read  Discrete Inputs
+		ReadRegistersOut = 0x03,			// Read  Holding Registers
+		ReadRegistersIn = 0x04,				// Read  Input Registers
+		WriteBit = 0x05,					// Write Single Coil
+		WriteRegister = 0x06,				// Write Single Holding Register
+		WriteBits = 0x0F,					// Write Multiple Coils
+		WriteRegisters = 0x10,				// Write Multiple Holding Registers
+		MaskRegister = 0x16,				// Mask Write Holding Register
+		ReadWriteRegisters = 0x17			// Read/Write Multiple Registers
 	};
 
-	// A normal Modbus Application Header. Every Modbus Packet begins with these 7 (+FuncCode) Bytes
+	// Modbus Application Header
+	// Every Modbus Packet begins with these 7 (+FuncCode) Bytes
 	_align(1) struct ModbusApHeader
 	{
 		word TxID;
@@ -30,6 +32,8 @@ variables
 		byte UnitID;
 		byte FuncCode;
 	};
+
+	/// Request structures following
 	// Read Data from the host. We only need the start address and the number of bits/registers we want to read
 	_align(1) struct ModbusReqRead
 	{
@@ -83,6 +87,7 @@ variables
 	};
 
 
+	/// Response structures following
 	// Receive several bit values
 	_align(1) struct ModbusResReceiveBits
 	{
@@ -120,16 +125,21 @@ variables
 		word Or;
 	};
 
+	// The maximum modbus telegram size.
+	// Several telegrams use this many bytes, but CAPL does not support a constant max function to let it calculate it. So we use ModbusResReceiveRegisters
 	const word gModbusMaxTelegramSize = __size_of(struct ModbusResReceiveRegisters);
 
 
+	// Some errors that may occur when sending a request
 	enum ModbusRequestError
 	{
-		Exception,
-		Timeout,
-		FinalTimeout,
-		NotSent
+		Exception,		// Modbus exception was returned
+		Timeout,		// Timeout occured, resending the packet
+		FinalTimeout,	// Timeout occured, not resending the packet
+		NotSent			// Sending the packet was impossible
 	};
+	
+	// Modbus exception codes according to Modbus Specification v1.1
 	enum ModbusException
 	{
 		None = 0x00,
@@ -142,6 +152,8 @@ variables
 		GatewayPathsNA = 0x0A,
 		TargetOffline = 0x0B
 	};
+	
+	// Fatal errors that may stop the code execution
 	enum FatalErrors
 	{
 		ParsingBuffer,