LatticeECP/EC and LatticeXP
Lattice Semiconductor
sysCLOCK PLL Design and Usage Guide
11-11
fINMIN = ((fVCOMIN / (V*N))*M, if below 25 * M round up to 25 * M
(9)
From the loop:
fINMAX = fPFDMAX * M = 420 * M
(10)
Assume fINMAX = 420
Equation (6) becomes:
fINMAX = (fVCOMAX / (V*N))*M, if above 420 round down to 420
(11)
From equation (1):
fOUTMIN = fINMIN * (N/M), if below 25 * N round up to 25 * N
(12)
fOUTMAX = fINMAX * (N/M), if above 420 round down to 420
(13)
fOUTKMIN = fOUTMIN / K
fOUTKMAX = fOUTMAX / K
Clock Distribution in LatticeECP/EC and LatticeXP
The clock inputs are selected from external I/Os, the sysCLOCK PLLs or general routing. These clock inputs are
fed through the chip via a clock distribution system.
LatticeECP/EC and LatticeXP devices provide a quadrant-based primary and secondary clock structure.
Primary Clock Sources and Distribution
Each quadrant has four primary clock nets: CLK0, CLK1, CLK2 and CLK3. CLK2 and CLK3 provide dynamic clock
selection (DCS) capability.
Figure 11-8 illustrates the block diagram of the primary clock distribution.
Figure 11-8. Primary Clocks and Center Switch Boxes
Note: Two PLLs are available in LatticeECP/EC/XP-6 or smaller devices.
Primary Clocks in Center Switch Box
PLL*: For LatticeECP/EC/XP-10 and larger devices
QUADRANT TL
QUADRANT TR
QUADRANT BL
QUADRANT BR
PCLKT7
PCLKT2
PLL*
CLKOP
CLKOS
CLKOK
PLL
CLKOP
CLKOS
CLKOK
PLL*
CLKOP
CLKOS
CLKOK
PLL
CLKOP
CLKOS
CLKOK
General
Routing
General
Routing
CLK0
CLK1
CLK2
CLK3
DCS
16:1
DCS
CLK3
CLK2
CLK1
CLK0
General
Routing
General
Routing
CLK0
CLK1
CLK2
CLK3
16:1
12:1 12:1 12:1 12:1
DCS
16:1
CLK3
CLK2
CLK1
CLK0
16:1
12:1 12:1 12:1 12:1
DCS
PCLKT0
PCLKT5