Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 7/08/2024
Public
Document Table of Contents

5.1.10. Waitrequest Allowance Adapter

The Waitrequest Allowance Adapter allows a connection between a host and an agent interface with different waitrequestAllowance properties.

The Waitrequest Allowance adapter provides the following features:

  • The adapter is used in the memory-mapped domain and operates with signals on the memory-mapped interface.
  • Signal widths and all properties other than waitrequestAllowance are identical on host and agent interfaces.
  • The adapter does not modify any command properties such as data width, burst type, or burst count.
  • The adapter is inserted by the Platform Designer interconnect software when a host and agent with different waitrequestAllowance property are connected.

When the agent has a waitrequestAllowance = n the host must deassert read or write signals after <n> transfers when waitrequest is asserted.

Table 49.  Interconnect Scenarios Requiring waitrequestAllowance
Host (m) / Agent (n) waitrequestAllowance Adaptation Required Description Adapter Function
m = n No

The host waitrequestAllowance is equal to the agent's waitrequestAllowance.

All signals are passed through.

m = 0; n > 0 Yes

The host cannot send when waitrequest=1, but holds the value on the bus. This would result in the agent receiving multiple copies.

Requires adaptation to prevent.

The adapter deasserts valid when input waitrequest is asserted.
m < n; m != 0 No

The host can send <m> transfers after waitrequest is asserted. The agent receives fewer than <n> transfers, which is acceptable.

All signals are passed through.
m > n; n = 0 Yes

The agent cannot accept transfers when waitrequest is asserted. Transfers sent when waitrequest=1 can be lost.

Prevention requires adaptation in the form of transfer buffering.

If the input waitrequest is asserted, the adapter buffers the input data.
m > n; n > 0 Yes

The agent cannot accept more than <n> transfers after waitrequest is asserted, however the host can send up to <m> transfers.

Transfers ( <m><n>) can be lost.

Prevention requires adaptation in the form of transfer buffering.

The adapter buffers the input data.