15.4. SIMPLE HANDSHAKE
RapidIO offers a very simple handshake protocol that provides the reliability that is required by systems without the burden of complex logic to support it. Although the details of the standard are outside the scope of this chapter, there are some very basic rules behind the protocol.
All transmitted packets are acknowledged with an acknowledgement control symbol.
Packets that contain errors are negatively acknowledged. Once a packet is negatively acknowledged, the transmitter requests input status information from the receiver and negotiates the link back into operation.
Packets that can not be accepted owing to buffering constraints are retried. Packets that are retried are automatically re-sent, based on the information transmitted in the retry control symbol.
These basic rules make up the framework of the handshake protocol and limit the complexity of logic design in the FPGA.
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