1.2.1 Flow Control

PCIe is a flow control-based protocol. Receivers advertise the supported number of receive buffers, and transmitters are not allowed to send TLPs without ensuring that sufficient receive buffer space is available. This control is provided by the 8 KB dedicated buffers included in the PCIESS receive and transmit channels.

Maximum Payload Size – The size of the TLP depends on the capabilities of both link partners. After the link is trained, the root complex sets the maximum payload size register (MAX_PAYLOAD_SIZE) value in the device control register. The maximum allowable payload size is 256 bytes.