当时就发现dqs走线不满足规范,dqs设计要求dqs + 200 -clock < 5mil ,但是板子上实际用到的dqs走线有两组超出比较明显,一个大于160 mil,一个大于 200 mil ,这会导致dqs数据会有延迟,但是考虑到内存训练
There are three critical decisions that forever complicated the DDR SDRAM memory controller. DLLs or equivalent circuits actually first appeared in some of the single data rate SDRAMs in the late 1990s to eliminate some of the clock insertion delay between the clock pin and the data output buffer...
A test signal is sent through a first number of delay books and a test is done as to whether it takes the test signal approximately a second pre-specified amount of time to pass the first number of delay books. Then, the number of delay books is increased or decreased by one at a ...
To maximize setup and hold constraints, the clock (DQS) is delayed internally using a delay locked loop that shifts the data 90 degrees with respect to the system clock. The data is latched using the DDIO circuitry. In output mode (writing to the RAM), the device sends the DQ signals ...
At least one of the bits is used to enable a data strobe preamble as either a default data strobe preamble of the memory or as a reduced data strobe preamble with a time length set equal to a fraction of the default preamble or a fraction of a clock cycle. The enabling bit can be ...
A method for calibrating read data strobe gating including the steps of: (A) performing a coarse timing adjustment configured to determine a coarse delay setting that produces invalid data, (B) performing a medium timing adjustment configured to adjust a medium delay setting and the coarse delay ...
# Input Constraints create_clock -name CLK_ddr_ldqs_INPUT -period $DDR_CLK_PERIOD create_clock -name virt_clk -period $DDR_CLK_PERIOD set_multicycle_path 0 -from virt_clk -to CLK_ddr_ldqs_INPUT set_input_delay -clock virt_clk $tDQSQ -max set_input_delay -clock virt_clk -$tQHmin...
I can see that within an IO cell, this clock path will have minimal delay, but how are the DQS/CQ clocks routed from the DQS pin I/O cell to the clock inputs of the DDIO registers in the DQ I/O blocks? 3) I’ve implemented a design using the ALT_DQ_DQS ...
For the actual buffer delay, refer to the respective device data sheet. These buffers have a fixed delay, which is not dependent on input clock frequency clock delay control circuit on each DQS pin allows a phase shift that center-aligns the incoming DQS signals within the data window of ...
This is the user-requested delay on the clock delay control block. Delay is specified either by number of delay buffers used or desired time delay. Time delay is converted to number of buffers during compilation. For the How should the delay chain be actual buffer delay, refer to the ...