Intel® Quartus® Prime Standard Edition User Guide: Platform Designer

ID 683364
Date 12/15/2018
Public
Document Table of Contents

3.1.11. Read and Write Responses

Platform Designer merges write responses if a write is converted (burst adapted) into multiple bursts. Platform Designer requires read response merging for a downsized (wide-to-narrow width adapted) read.

Platform Designer merges responses based on the following precedence rule:
DECERR > SLVERR > OKAY > EXOKAY

Adaptation between a master with write responses and a slave without write responses can be costly, especially if there are multiple slaves, or if the slave supports bursts. To minimize the cost of logic between slaves, consider placing the slaves that do not have write responses behind a bridge so that the write response adaptation logic cost is only incurred once, at the bridge’s slave interface.

The following table describes what happens when there is a mismatch in response support between the master and slave.

Table 29.  Response Support for Mismatched Master and Slave
  Slave with Response Slave Without Response
Master with Response

Interconnect delivers response from the slave to the master.

Response merging or duplication may be necessary for bus sizing.

Interconnect delivers an OKAY response to the master
Master without Response Master ignores responses from the slave No need for responses. Master, slave and interconnect operate without response support.
Note:

If there is a bridge between the master and the endpoint slave, and the responses must come from the endpoint slave, ensure that the bridge passes the appropriate response signals through from the endpoint slave to the master.

If the bridge does not support responses, then the responses are generated by the interconnect at the slave interface of the bridge, and responses from the endpoint slave are ignored.

For the response case where the transaction violates security settings or uses an illegal address, the interconnect routes the transactions to the default slave. For information about Platform Designer system security, refer to Manage System Security. For information about specifying a default slave, refer to Error Response Slave in Platform Designer System Design Components.

Note: Avalon® -MM slaves without a response signal are not able to notify a connected master that a transaction has not completed successfully. As a result, Platform Designer interconnect generates an OKAY response on behalf of the Avalon® -MM slave.