Transaction handling

A transaction handling method comprising:

• storing data defining each transaction issued by one or more transaction master devices;
• controlling routing of a transaction response to a given transaction either to a response buffer operable to buffer the transaction response or as an output to the transaction master device which issued the given transaction;
• accessing data for each buffered transaction response indicating a previously issued transaction on which that buffered transaction response depends;
• outputting the buffered transaction response to the transaction master device which issued that transaction when the previously issued transaction has already been output by the apparatus;
• mapping each transaction to a transaction index;
• storing, for a given transaction, data defining the transaction index of a previous transaction on which the given transaction is dependent;
• storing the indicator to indicate whether, for the given transaction, the response to the previous transaction has been output;
• and
• buffering a transaction response received in respect of the given transaction at least until the indicator indicates that a response to the previous transaction has been output.

Transaction handling apparatus comprising:

• means for buffering transaction responses;
• means for storing data defining each transaction issued by one or more transaction master means;
• means for controlling routing of a transaction response to a given transaction either to a means for buffering or as an output to the transaction master means which issued the given transaction;
• means for accessing data for each buffered transaction response indicating whether a response has been output by the apparatus for a previously issued transaction on which that buffered transaction response depends;
• means for outputting the buffered transaction response to the transaction master means which issued that transaction when the previously issued transaction has already been output by the apparatus;
• means for mapping each transaction to a transaction index;
• means for storing, for a given transaction, data defining the transaction index of a previous transaction on which the given transaction is dependent;
• means for storing the indicator to indicate whether, for the given transaction, the response to the previous transaction has been output;
• and
• means for buffering a transaction response received in respect of the given transaction at least until the indicator indicates that a response to the previous transaction has been output.