
Chapter 10: Transaction Layer Protocol (TLP) Details 10–3
Transaction Layer Routing Rules
December 2013 Altera Corporation Cyclone V Hard IP for PCI Express
User Guide
Transaction Layer Routing Rules
Transactions adhere to the following routing rules:
■ In the receive direction (from the PCI Express link), memory and I/O requests that
match the defined base address register (BAR) contents and vendor-defined
messages with or without data route to the receive interface. The Application
Layer logic processes the requests and generates the read completions, if needed.
■ In Endpoint mode, received Type 0 Configuration requests from the PCI Express
upstream port route to the internal Configuration Space and the Cyclone V Hard
IP for PCI Express generates and transmits the completion.
■ The Hard IP handles supported received message transactions (Power
Management and Slot Power Limit) internally. The Endpoint also supports the
Unlock and Type 1 Messages. The Root Port supports Interrupt, Type 1 and error
Messages.
■ Vendor-defined Type 0 Message TLPs are passed to the Application Layer.
■ The Transaction Layer treats all other received transactions (including memory or
I/O requests that do not match a defined BAR) as Unsupported Requests. The
Transaction Layer sets the appropriate error bits and transmits a completion, if
needed. These Unsupported Requests are not made visible to the Application
Layer; the header and data is dropped.
Hot Plug Messages
Attention_indicator On Transmit Receive No Yes No
As per the recommendations in the
PCI
Express Base Specification Revision 2.1
,
these messages are not transmitted to the
Application Layer.
Attention_Indicator
Blink
Transmit Receive No Yes No
Attention_indicator_
Off
Transmit Receive No Yes No
Power_Indicator On Transmit Receive No Yes No
Power_Indicator Blink Transmit Receive No Yes No
Power_Indicator Off Transmit Receive No Yes No
Attention
Button_Pressed
(1)
Receive Transmit No No Yes
Notes to Table 10–1:
(1) In Endpoint mode.
(2) In the PCI Express Base Specification Revision 2.1, this message is no longer mandatory after link training.
Table 10–1. Supported Message Types
(2)
(Part 3 of 3)
Message
Root
Port
Endpoint
Generated by
Comments
App
Layer
Core
Core (with
App Layer
input)
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