Visible to Intel only — GUID: irb1676546027638
Ixiasoft
Visible to Intel only — GUID: irb1676546027638
Ixiasoft
3.2.1.2. Output Path
Component | Description |
---|---|
Pipeline Registers | Represent pipeline stages in the output path. |
TX FIFO | Stores the data to be transmitted out. |
Shift Register | Delays the enable signal at the read side of the TX FIFO at VCO cycle increment. |
Phase Shift | Delays TX data and strobe at 1/128 of a VCO cycle increments. |
There are two types of delays in the output path, namely inherent latency and output delay, TxDqDelay.
Delay | Type | Description |
---|---|---|
Inherent latency | Static | Captured in the pipeline stages from the assertion of the output enable in the core (group_<n>_oe_from_core[]) until the data go into TX FIFO. The parameter Additional Write Latency in the IP Parameter Editor is added to the inherent latency. |
TxDqDelay delay (output delay) | Dynamic | You can configure this 11-bit wide register in the control registers. The TxDqDelay register consists of two parts, as described in the next table. The integer part of the delay uses a shift register to delay the enable signal that goes to the read side of TX FIFO. |
Feature | Description | Min | Max |
---|---|---|---|
TxDqDelay [10:7] |
Integer number of VCO clock cycles. The integer portion of the delay is accomplished using a shift register to delay the enable signal that goes to the read side of the TX FIFO. | 0 | 15 |
TxDqDelay [6:0] |
Additional phase shift measured in 1/128 of VCO clock period. | 0 | 127 |
The preceding figure shows an example of TX data transfer in QR DDR. The data_from_core for each pin is 8 bits wide. To enable one extra preamble cycle before the data starts, wait for strobe_out_en to transition from 0 to h8 in one core clock cycle before the oe_from_core signal, as shown in the figure. Setting Output strobe phase to 90 degrees causes the PHY Lite IP to send the data center aligned.