DQS Write Operation
The driver asserting the dqs_enable signal at 18.803 ms begins the write operation. The dqs_write signal is asserted at 18.811 ms. The write_oe_in signal of the ALTDQ_DQS2 IP core is set to high and is ready to send data to the DQS agent. Data are written to the dqs_writedata of the DQS driver and then reflected in the dq signal of the ALTDQ_DQS2 IP core. The data written out from the DQS driver are stored in check_fifo. The dqs_write signal deasserts at 18.851 ms. The dqs_enable deasserts at 18.859 ms. Outgoing data from the ALTDQ_DQS2 (dq) is center aligned to the write clock (dqs_ios_to_agent).
The following figure shows the DQS write operation waveform.
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 ms and 18.851 ms. Centre aligned output data appears on read_write_data_io between 18.822 ms and 18.86 2 ms. 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.
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