ECP5 and ECP5-5G High-Speed I/O Interface
Technical Note
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FPGA-TN-02035-1.3
The values for tDVBCKGDDR and tDVACKGDDR can be picked up from the External Switching Characteristics section of
ECP5 and ECP5-5G Family Data Sheet (FPGA-DS-02012)
for the MAX speed.
Preference Example:
For GDDRX1_TX.SCLK.Centered interface running at 250 MHz, tDVB_GDDRX1 = tDVA_GDDRX1 = 0.67 ns, the
preference would be –
CLOCK_TO_OUT PORT "dataout" MAX -0.670000 ns MIN -1.330000 ns CLKPORT "clk" CLKOUT PORT "clkout”;
Note
: Refer to
ECP5 and ECP5-5G Family Data Sheet (FPGA-DS-02012)
for the latest tDVAGDDR and Tdvbgddr numbers.
5.13.3.2.
Transmit Aligned Interfaces
In this case, the clock and data are aligned when leaving the device.
shows the timing diagram for this
interface.
tDIAGDDR = Data valid after clock.
tDIBGDDR = Data valid before clock.
Transmit Parameters
CLK
Data (TDAT, TCTL)
t
DIAGDDR
t
DIBGDDR
t
DIBGDDR
t
DIAGDDR
Figure 5.20. Transmit Aligned Interface Timing
shows that max value after which the data cannot transition is tDIA_GDDRX1/X2. The min value before
which the data cannot transition is – tDIB_GDDRX1/X2. Negative sign is used for the min value is because in this
particular case the min condition occurs before the clock edge.
The clock to out time in the software can be specified as –
CLOCK_TO_OUT PORT “dataout” MAX <tDIA_GDDRX1/X2> MIN <-tDIB_GDDRX1/X2> CLKPORT “clk” CLKOUT PORT
“clk”;
where:
Data = Data Output Port
Clock = Forwarded Clock Output Port
clk = Input Clock Port
Both tDIA_GDDRX1/X2 and tDIB_GDDRX1/X2 numbers are available in the External Switching Characteristics section of
ECP5 and ECP5-5G Family Data Sheet (FPGA-DS-02012)
for maximum speed.
Preference Example:
For GDDRX2_TX.Aligned case running at 400 MHz, tDIA_GDDRX2= tDIB_GDDRX2=0.16 ns. The preference would be –
CLOCK_TO_OUT PORT "dataout" MAX 0.16 ns MIN -0.16 ns CLKPORT "clk" CLKOUT PORT "clkout”;
Note
: Refer to
ECP5 and ECP5-5G Family Data Sheet (FPGA-DS-02012)
for the latest tDIA_GDDX1/X2 and
tDIB_GDDRX1/X2 numbers.