ECP5 and ECP5-5G High-Speed I/O Interface
Technical Note
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16
FPGA-TN-02035-1.3
5.2.
GDDRX1_RX.SCLK.Aligned
This a Generic 1x gearing Receive interface using SCLK. The clock is coming in edge aligned to the data. This interface
must be used for speeds below 250 MHz.
This DDR interface uses the following modules:
IDDRX1F element to capture the data
DDRDLLA/DLLDELD blocks are used to phase shift the incoming clock going to primary clock tree (SCLK).
Static data delay element DELAYG is used to delay the incoming data enough to remove the clock injection time.
Optionally, you can choose to use Dynamic Data Delay adjustment using DELAYF element to control the delay on
the DATA dynamically. DELAYF also allows you to override the input delay set. The type of delay required can be
selected through Clarity Designer.
DEL_MODE attribute is used with DELAYG and DELAYF element to indicate the interface type so that the correct
delay value can be set in the delay element.
Dynamic Margin adjustment in the DDRDLLA module can be optionally used to adjust the DDRDLLA delay
dynamically.
The output of the DLLDELD module is also used as the clock input to the DDRDLLA which sends the delay values to the
DLLDELD module. The Receiver Synchronization (RX_SYNC) soft IP is required for the aligned interfaces to prevent
stability issues that may occur due to this loop at startup. The soft IP prevents any updates to the DLLDELD at start until
the DDRDLLA is locked. Once locked the DLLDELD is updated and FREEZE on the DDRDLL is removed. This soft IP is
automatically generated by Clarity Designer.
The following figures show the static delay and dynamic delay options for this interface.
ID D R X 1F
S C L K
D
Q 0
Q 1
R S T
D atain
Q [0]
Q [1]
C lkin
A
D E L A Y G
Z
D L L D E L D
Z
A
D D R D E L
L O AD N
MO V E
D IR E C T IO N
C F L AG
C L K
R S T
UD D C NT L N
F R E E Z E
D D R D E L
L O C K
D D R D L L A
D C NT L [7:0]
“
0
”
“
0
”
(open)
P rimary
D E L _MO D E =
S C L K _AL IG NE D
R eady
S T O P
D L L _L O C K
F R E E Z E
UD D C NT L N
D L L _R E S E T
D D R _R E S E T
S Y NC _C L K
R S T
UP D AT E
S ync_clk
S ync_res et
Update
R E AD Y
(open)
R X _S Y NC
S clk
D cntl[7:0]
Figure 5.3. GDDRX1_RX.SCLK.Aligned Interface (Static Delay)