Intel IXF1104 manual 2.9 SPI3 Flow Control, RX SPI3 Flow Control, TX SPI3 Flow Control

Intel® IXF1104 4-Port Gigabit Ethernet Media Access Controller

5.2.2.8.2Parity

The IXF1104 MAC can be odd or even (the IXF1104 MAC defaults to odd) when calculating parity on the data bus. This can be changed to accommodate even parity if desired, and can be set for transmit and receive ports independently. The RX and TX parity sense bits have a direct relationship to the port parity in SPHY mode.

The per port RX parity is set in the “SPI3 Receive Configuration ($0x701)" and the per port TX Parity is set in the “SPI3 Transmit and Global Configuration ($0x700)".

5.2.2.9SPI3 Flow Control

The SPI3 packet interface supports transmit and receive data transfers at clock rates independent of the line bit rate. As a result, the IXF1104 MAC supports packet rate decoupling using internal FIFOs. These FIFOs are 10 KB per port in the transmit direction (egress from the IXF1104 MAC to the line interfaces) and 32 KB per port in the receive direction (ingress to the IXF1104 MAC from the line interfaces).

Control signals are provided to the network processor and the IXF1104 MAC to allow either one to exercise flow control. Since the bus interface is point-to-point, the receive interface of the IXF1104 MAC pushes data to the link-layer device. For the transmit interface, the packet available status granularity is byte-based.

5.2.2.9.1RX SPI3 Flow Control

In the receive direction, when the IXF1104 MAC has stored an end-of-packet (a complete small packet or the end of a larger packet) or some predefined number of bytes in its receive FIFO, it sends the in-band address followed by FIFO data to the link-layer device (in MPHY mode). The data on the interface bus is marked with the valid signal (RVAL) asserted. The network processor device can pause the data flow by de-asserting the Receive Read Enable (RENB) signal.

RENB_0:3

RENB_0:3 controls the flow of data from the IXF1104 MAC RX FIFOs. In SPHY mode, there is a dedicated RENB for each port. In MPHY mode, RENB_0 is used as the global signal covering all ports. When RENB is sampled Low, the network processor can accept data. A read is performed from the RX FIFO and the RDAT, RPRTY, RMOD[1:0], RSOP, REOP, RERR, RSX, and RVAL signals are updated on the following rising edge of RFCLK.

RENB can be asserted High by the Network Processor at any time if it is unable to accept any more data. When the RENB is sampled High by the IXF1104 MAC, a read of the RX FIFO is not performed, and the RDAT, RPRTY, RMOD[1:0], RSOP, REOP, RERR, RSX and RVAL signals remain unchanged on the following rising edge of RFCLK.

5.2.2.9.2TX SPI3 Flow Control

In the transmit direction, when the IXF1104 MAC has space for some predefined number of bytes in its transmit FIFO, it informs the Network Processor device by asserting one of the Transmit Packet Available (TPA) signals. The Network Processor device writes the in-band address followed by packet data to the IXF1104 MAC using an enable signal (TENB). The network processor device monitors the TPA signals for a High-to-Low transition, which indicates that the transmit FIFO is almost full (the number of bytes left in the FIFO is user-selectable by setting the “TX FIFO High Watermark Ports 0 - 3 ($0x600 – 0x603)", and suspends data transfer to avoid an overflow. The Network Processor device can pause the data flow by de-asserting the enable signal (TENB).

91 Datasheet

Document Number: 278757

Revision Number: 009

Revision Date: 27-Oct-2005