Coupled MAC+PCS mode is often described as standard Fixed Ethernet (FixedE) mode. When configured in this mode, the AXI4-Stream interface operates in non-channelized segmented mode that ensures high throughput over a range of traffic profiles. The interface is dynamically reconfigurable during run-time to support multiple modes of Ethernet operation. The DCMAC Subsystem AXI4-Stream interface supports up to a total of 600 Gb/s bandwidth. It can be configured as six independent 100 Gb/s AXI4-Stream interfaces. Alternatively, the portions of the AXI4-Stream interface can be ganged together to deliver individual AXI4-Stream interface rates of 200 Gb/s or 400 Gb/s, as well as combinations of 100 Gb/s, 200 Gb/s and 400 Gb/s.
- The c0_ctl_tx_data_rate, c2_ctl_tx_data_rate, and c4_ctl_tx_data_rate fields of the C0_TX_MODE_REG, C2_TX_MODE_REG, and C4_TX_MODE_REG for TX.
- The c0_ctl_rx_data_rate, c2_ctl_rx_data_rate, and c4_ctl_rx_data_rate fields of the C0_RX_MODE_REG, C2_RX_MODE_REG, and C4_RX_MODE_REG registers for RX.
The AXI clock frequencies in the following table are required to meet bandwidth for a given Ethernet interface.
You can use a lower frequency AXI clock to ease timing closure in some device speed grades. To allow use of a reduced clock frequency, a special mode exists that doubles the width of each 100GE AXI4-Stream interface to 512 bits while reducing to three the number of distinct 100GE AXI4-Stream interfaces. This mode is entered using the control fields ctl_tx_axis_cfg and ctl_rx_axis_cfg of the GLOBAL_MODE register. In addition, the control fields ctl_tx_pcs_active_ports and ctl_rx_pcs_active_ports of the same register must be set appropriately.
Data Rate | Nominal Clock Frequency (MHz) | AXI4-Stream Data Width (Bits) | ctl_tx_axis_cfg / ctl_rx_axis_cfg | c<N>_ctl_tx_data_rate / c<N>_ctl_rx_data_rate | ||
---|---|---|---|---|---|---|
N=0 | N=2 | N=4 | ||||
6 x 100GE | 390.625 | 6 x 256 | 0 | 2'b00 | 1'b0 | 1'b0 |
3 x 200GE | 390.625 | 3 x 512 | 0 | 2'b01 | 1'b1 | 1'b1 |
1 x 400GE 1 x 200GE |
390.625 |
1 x 1024 1 x 512 |
0 | 2'b10 | N/A | 1'b1 |
1 x 400GE 2 x 100GE |
390.625 |
1 x 1024 2 x 256 |
0 | 2'b10 | N/A | 1'b0 |
1 x 200GE 4 x 100GE |
390.625 |
1 x 512 4 x 256 |
0 | 2'b01 | 1'b0 | 1'b0 |
... | ... | ... | ... | ... | ... | ... |
3 x 100GE | 195.313 | 3 x 512 | 1 | 2'b00 | 1'b0 | 1'b0 |