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Calculate PDU size constraints

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This commit is contained in:
Michael Croes
2018-06-22 20:49:12 +02:00
parent 47cce5887d
commit 2a4485941f
3 changed files with 37 additions and 14 deletions
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11
S7.Net/PlcSynchronous.cs
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@@ -374,6 +374,8 @@ namespace S7.Net
/// <param name="dataItems">The DataItem(s) to write to the PLC.</param>
public void Write(params DataItem[] dataItems)
{
AssertPduSizeForWrite(dataItems);
var message = new ByteArray();
var length = S7WriteMultiple.CreateRequest(message, dataItems);
stream.Write(message.Array, 0, length);
@@ -479,15 +481,10 @@ namespace S7.Net
/// <param name="dataItems">List of dataitems that contains the list of variables that must be read. Maximum 20 dataitems are accepted.</param>
public void ReadMultipleVars(List<DataItem> dataItems)
{
int cntBytes = dataItems.Sum(dataItem => VarTypeToByteLength(dataItem.VarType, dataItem.Count));
//TODO: Figure out how to use MaxPDUSize here
//Snap7 seems to choke on PDU sizes above 256 even if snap7
//replies with bigger PDU size in connection setup.
if (dataItems.Count > 20)
throw new Exception("Too many vars requested");
if (cntBytes > 222)
throw new Exception("Too many bytes requested"); // TODO: proper TDU check + split in multiple requests
AssertPduSizeForRead(dataItems);
try
{
// first create the header