24
ECP5 and ECP5-5G sysCLOCK
PLL/DLL Design and Usage Guide
For a very small clock domain, the user can limit the distance of a general routing based (gated) clock to one PLC
in distance to the logic it clocks. The user must group this logic (UGROUP) with a BBOX = “1, 1” (see Diamond
Help > Constraints Reference Guide > Preferences > UGROUP) as well as specify a “PROHIBIT PRIMARY” on the
generated clock. If the software cannot place the logic tree within the BBOX, then an error message will occur.
Figure 22. Gated Clock to Small Logic Domain
General routing PCLK pins
Some Dedicated pins (GR_PCLK) can access some CIBs along the edge of the device and can drive the primary
clock routing from this CIB. These will go through some general routing but have direct access to the primary clock
from this dedicated CIB. There are four at the left side and right side, four at the top side of the device. These pins
can be used when user runs out of PCLK pins. Note that for any DDR interface, it is still required to use dedicated
clock pins and clock trees.
sysCLOCK PLL
The ECP5 and ECP5-5G PLL provides features such as clock injection delay removal, frequency synthesis, and
phase adjustment. Figure 23 shows a block diagram of the ECP5 and ECP5-5G PLL.
Figure 23. ECP5 and ECP5-5G PLL Block Diagram
Clock
So
u
rce
General
Ro
u
ting
General
Ro
u
ting
1 PLC
General
Ro
u
ting
Logic
Logic
Logic
Logic
Refclk Di
v
ider M
Phase
Detector,
VCO, and
Loop Filter
CLKOP
Di
v
ider
(1-12
8
)
Lock
Detect
Feed
b
ack
Clock Di
v
ider
CLK0
CLK1
SEL
Refclk
E
N
CLKOP
CLKOP
CLKOS
CLKOS2
CLKOS3
CLKI
PLLCSOUT
PLLREFCS
VCO
CLKFB
FBKSEL
CLKOS
Di
v
ider
(1-12
8
)
CLKOS2
Di
v
ider
(1-12
8
)
CLKOS3
Di
v
ider
(1-12
8
)
VCO
VCO
VCO
Internal Feed
b
ack
CLKOP, CLKOS, CLKOS2, CLKOS3
RST
STDBY
PHASESTEP
PHASEDIR
PHASESEL[1:0]
Dynamic
Phase
Adj
u
st
PHASELOADREG
LOCK
E
N
CLKOS
E
N
CLKOS2
E
N
CLKOS3
CLKI
CLKI2