LFSC datasheet(16/237 Pages) LATTICE

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2-12

Architecture

Lattice Semiconductor

LatticeSC/M Family Data Sheet

There is a Digital Control (DCNTL) bus available from the DLL block. This Digital Control bus is available to the

delay lines in the PIC blocks in the adjacent banks. The UDDCNTL signal allows the user to latch the current value

on the digital control bus.

Figure 2-12 shows the DLL block diagram of the DLL inputs and outputs. The output of the phase frequency detec-

tor controls an arithmetic logic unit (ALU) to add or subtract one delay tap. The digital output of this ALU is used to

control the delay value of the delay chain and this digital code is transmitted via the DCNTL bus.

The sysCLOCK DLL can be conﬁgured at power-up, then, if desired, reconﬁgured dynamically through the Serial

Memory Interface bus which interfaces with the on-chip Microprocessor Interface (MPI) bus. In addition, users can

drive the SMI interface from routing if desired.

The user can conﬁgure the DLL for many common functions such as clock injection match and single delay cell.

Lattice provides primitives in its design for time reference delay (DDR memory) and clock injection delay removal.

Figure 2-12. DLL Diagram

PLL/DLL Cascading

The LatticeSC devices have been designed to allow certain combinations of PLL and DLL cascading. The allow-

able combinations are as follows:

• PLL to PLL

• PLL to DLL

• DLL to DLL

• DLL to PLL

DLLs are used to shift the clock in relation to the data for source synchronous inputs. PLLs are used for frequency

synthesis and clock generation for source synchronous interfaces. Cascading PLL and DLL blocks allows applica-

tions to utilize the unique beneﬁts of both DLL and PLLs.

When cascading the DLL to the PLL, the DLL can be used to drive the PLL to create ﬁne phase shifts of an input

clock signal. Figure 2-13 shows a shift of all outputs for CLKOP and CLKOS out in time.

CLKI

CLKFB

CLKOP

CLKOS

UDDCNTL

ALUHOLD

DCNTL

Delay

Chain

ALU

Duty50

Phase Adj

PFD

DCNTL

Gen

LOCK

Phase Adj

RSTN

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