
Figure 33: DQS Write Operation Waveform
Note: Before and after the DQS write operation, the dq signal is in Hi-Z mode to filter any unwanted
glitch on the bidirectional port.
The following figure shows the waveform after executing the topwave.do file. The write_oe_in signal is
held high throughout the five sets of valid write_data_in between 18.811 µs and 18.851 µs. Centre
aligned output data appears on read_write_data_io between 18.822 µs and 18.86 2µs. The
output_strobe_out is a free running clock while the read_write_data_io is driven at Hi-Z when there
is no data transaction.
Figure 34: DQS Write Operation Waveform After Executing the topwave.do File
Side Read Operation
The side read operation is performed between 18.923 µs and 18.963 µs. The DQS agent sends data to the
DQS driver with the side_readdata signal. Data validation is carried out in parallel, by comparing the
side_readdata signal against the content of the check/i/o (data which was written out during the DQS
write operation). If there is a mismatch, the software generates an error message.
The following figure shows the waveform for the side read operation.
Figure 35: Side Read Operation Waveform
Side Write Operation
The side write operation begins between 19.011 µs and 19.067 µs. The data written out from the DQS
driver is also stored in check/i/o.
UG-01089
2014.12.17
Side Read Operation
69
ALTDQ_DQS2 IP Core User Guide
Altera Corporation
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