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ECP5 and ECP5-5G sysCLOCK
PLL/DLL Design and Usage Guide
DCS Timing Diagrams
Figure 10 shows timing diagrams to show the operation of the DCS in Glitchless mode in conjunction with the DCS-
MODE attribute.
Figure 10. Timing Diagrams by “DCSMODE” Attribute Setting, Glitchless Operation (MODESEL=’0’)
CLK0
CLK1
SEL[3:0]
“0001”
“0010”
DCSOUT
“0001”
SEL[3:0] Changes to “0010”:
- Wait for CLK0 rising edge.
- Switch output at CLK1 rising edge.
SEL[3:0] Changes to “0001”:
- Wait for CLK1 rising edge.
- Switch output at CLK0 rising edge.
DCSMODE = “POS”
CLK0
CLK1
SEL[3:0]
“0001”
“0010”
DCSOUT
“0001”
SEL[3:0] Changes to “0010”:
- Wait for CLK0 falling edge.
- Switch output at CLK1 falling edge.
SEL[3:0] Changes to “0001”:
- Wait for CLK1 falling edge.
- Switch output at CLK0 falling edge.
DCSMODE = “NEG”
CLK0
SEL[3:0]
“0001”
“0010”
- Switch low @CLK0 falling edge.
- The attribute name indicates which clock will toggle. Other
values of SEL will cause the output to remain low.
- SEL must not change during setup prior to rising clock.
DCSMODE = “CLK<0-3>_LOW”
DCSOUT
CLK0
SEL[3:0]
“0001”
“0010”
- Switch low @CLK0 rising edge.
- The attribute name indicates which clock will toggle. Other
values of SEL will cause the output to remain high.
- SEL must not change during setup prior to rising clock.
DCSMODE = “CLK<0-3>_HIGH”
DCSOUT