Altera Interlaken MegaCore Function - Manual (Page 40)

4–14 Chapter 4: Functional Description
Transmit Path
Interlaken MegaCore Function June 2012 Altera Corporation
User Guide
MegaCore function to insert idle symbols on the Interlaken link. Figure 4–10 shows
the end of the 1016-byte packet on tx_ch0_datain_data, and the resulting non-zero
value of tx_ch0_datain_empty. This example does not illustrate use of a non-zero
empty signal partway through a packet transfer, although the arbiter does check the
empty signal on every clock cycle in which valid data is transfered.
Figure 4–8 shows the application utilizing the Interlaken link fully. The Interlaken
MegaCore function backpressures the application to prevent overflow, by deasserting
the tx_ch0_datain_ready signal. When it is ready to accept data again, it reasserts the
tx_ch0_datain_ready signal, and the channel can resume sending new data.
Figure 4–7. Beginning of 1016-Byte Packet Transfer on Channel 0
tx_mac_c_clk
tx_ch0_datain_ready
tx_ch0_datain_valid
tx_ch0_datain_data[127:0]
tx_ch0_datain_empty[3:0]
tx_ch0_datain_startofpacket
tx_ch0_datain_endofpacket
tx_ch0_datain_error
B0-B15 B16-B31 B32-B47 B48-B63
4h'0 4h'0 4h'0 4h'0
Figure 4–8. Full Link Utilization During 1016-Byte Packet Transfer on Channel 0
tx_mac_c_clk
tx_ch0_datain_ready
tx_ch0_datain_valid
tx_ch0_datain_data[127:0]
tx_ch0_datain_empty[3:0]
tx_ch0_datain_startofpacket
tx_ch0_datain_endofpacket
tx_ch0_datain_error
4h'0 4h'0 4h'0 4h'0 4h'0 4h'0 4h'0 4h'0