Architecture
LatticeECP2/M Family Data Sheet
Lattice Semiconductor
Delay Locked Loops (DLL)
In addition to PLLs, the LatticeECP2/M family of devices has two DLLs per device.
CLKI is the input frequency (generated either from the pin or routing) for the DLL. CLKI feeds into the output muxes
block to bypass the DLL, directly to the DELAY CHAIN block and (directly or through divider circuit) to the reference
input of the Phase Frequency Detector (PFD) input mux. The reference signal for the PFD can also be generated
from the Delay Chain and CLKFB signals. The feedback input to the PFD is generated from the CLKFB pin, CLKI
or from tapped signal from the Delay chain.
The PFD produces a binary number proportional to the phase and frequency difference between the reference and
feedback signals. This binary output of the PFD is fed into a Arithmetic Logic Unit (ALU). Based on these inputs,
the ALU determines the correct digital control codes to send to the delay chain in order to better match the refer-
ence and feedback signals. This digital code from the ALU is also transmitted via the Digital Control bus (DCNTL)
bus to its associated DLLDELA delay block. The ALUHOLD input allows the user to suspend the ALU output at its
current value. The UDDCNTL signal allows the user to latch the current value on the DCNTL bus.
The DLL has two independent clock outputs, CLKOP and CLKOS. These outputs can individually select one of the
outputs from the tapped delay line. The CLKOS has optional fine phase shift and divider blocks to allow this output
to be further modified, if required. The fine phase shift block allows the CLKOS output to phase shifted a further 45,
22.5 or 11.25 degrees relative to its normal position. Both the CLKOS and CLKOP outputs are available with
optional duty cycle correction. Divide by two and divide by four frequencies are available at CLKOS. The LOCK out-
put signal is asserted when the DLL is locked. Figure 2-6 shows the DLL block diagram and Table 2-5 provides a
description of the DLL inputs and outputs.
The user can configure the DLL for many common functions such as time reference delay mode and clock injection
removal mode. Lattice provides primitives in its design tools for these functions. For more information about the
DLL, please see the list of additional technical documentation at the end of this data sheet.
Figure 2-6. Delay Locked Loop Diagram (DLL)
Delay Chain
Duty
Cycle
50%
ALUHOLD
Delay0
CLKOP
CLKOS
Delay1
Delay2
Output
Muxes
÷4
÷2
Duty
Cycle
50%
(from routing
or external pin)
Reference
Phase
Frequency
Detector
Delay3
Delay4
CLKI
Arithmetic
Logic Unit
÷4
÷2
from CLKOP (DLL
internal), from clock net
(CLKOP) or from a user
clock (pin or logic)
Feedback
LOCK
Lock
Detect
CLKFB
Digital
DCNTL
9
Control
Output
UDDCNTL
RSTN
2-8
LATTICE [ LATTICE SEMICONDUCTOR ]
