ID 683385
Date 5/08/2017
Public

## 7.4.9.2. Equations for QDR-IV Board Skew Parameters

Table 288.  Parameter Equations
Parameter Description/Equation
Maximum system skew within address/command bus The largest skew between the address and command signals. Enter combined board and package skew.
Average delay difference between address/command and CK

The average delay difference between the address and command signals and the CK signal, calculated by averaging the longest and smallest Address/Command signal delay minus the CK delay. Positive values represent address and command signals that are longer than CK signals and negative values represent address and command signals that are shorter than CK signals. The Quartus Prime software uses this skew to optimize the delay of the address and command signals to have appropriate setup and hold margins.

Maximum System skew within QK group

The largest skew between all DQ and DM pins in a QK group. Enter combined board and package skew. This value affects the read capture and write margins.

Where n includes both DQa and DQb
Maximum CK delay to device

The delay of the longest CK trace from the FPGA to any device.

where n is the number of memory clocks.
Maximum DK delay to device

The delay of the longest DK trace from the FPGA to any device.

where n is the number of DK.
Average delay difference between DK and CK

The average delay difference between the DK signals and the CK signal, calculated by averaging the longest and smallest DK delay minus the CK delay. Positive values represent DK signals that are longer than CK signals and negative values represent DK signals that are shorter than CK signals. The Quartus Prime software uses this skew to optimize the delay of the DK signals to have appropriate setup and hold margins.

CDO:/content/authoring/rto1474984235656.xmlwhere n is the number of memory clocks and m is the number of DK.
Maximum skew between DK groups

The largest skew between DK signals in different DK groups.

where n is the number of DK. Where n includes both DQa and DQb.