SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The PSI-L is used to transfer words of packet data and control information between two peer entities via direct connection. There are credits used for flow control to guarantee that blocking does not occur between threads. Multiple packet transfers can be ongoing simultaneously across a PSI-L interface each on a separate logical thread but all sharing a single datapath through time division multiplexing. Each packet which is transferred is accompanied by a destination thread ID which indicates the logical destination thread to which the packet is being sent.
There is low level hardware handshake between PSI-L master and slave used for transfering data. As it is blocking by nature, a higher level protocol is also used in which credits are maintained for each thread connection. Moments of non-readiness are allowed on the interface but there is no possibility that one thread can block another for an indefinite time since a thread must have credit for the destination before it is allowed to use the interface.
Figure 10-23 illustrates the point to point PSI-L connection.
PSI-L is intended to be a versatile interface which can carry various types of communications. Table 10-134 describes several types of threads which have been defined.
Type | Description | Example Endpoints |
---|---|---|
Queue Management (QM) Messaging | Provides transport for queue push, pop, and divert messages to support distributed queue based work passing | Centralized queue manager or message manager and distributed DMA clients |
Direct IO | Allows for tunneling CBASS compatible bus transactions through a PSI interconnect | Module which has no CBASS master to a remote proxy block |
DMA Control Transport | Provides transport for DMA transfer descriptions from a source thread to a destination thread | DMA channel controller to DMA transfer controller |
DMA Data Transport | Provides transport for packed data from a source thread to a destination thread | Packet oriented module like networking adapters to or from centralized DMA |
Each thread on PSI-L is established between a single thread master and a single thread slave using a connection oriented transfer mechanism. A thread master and a thread slave are "paired" to create a logical connection between them referred to as a thread. Pairing is accomplished using a Pair Configuration Message which is valid in all thread types. Pairing can only occur between a thread master and a thread slave of the same type.