LFE2-50E-VID-EV Lattice, LFE2-50E-VID-EV Datasheet - Page 40

• Manufacturer Part Number: LFE2-50E-VID-EV
• Description: Development Software LatticeECP2 Video Dev Kit
• Manufacturer: Lattice

Specifications of LFE2-50E-VID-EV

• Tool Type: Development Software Kit
• Core Architecture: CPLD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Lattice Semiconductor
Figure 2-34. DQS Input Routing for the Bottom Edge of the Device
DLL Calibrated DQS Delay Block
Source synchronous interfaces generally require the input clock to be adjusted in order to correctly capture data at
the input register. For most interfaces a PLL is used for this adjustment. However, in DDR memories the clock
(referred to as DQS) is not free-running so this approach cannot be used. The DQS Delay block provides the
required clock alignment for DDR memory interfaces.
The DQS signal (selected PIOs only, as shown in Figure 2-35) feeds from the PAD through a DQS delay element to
a dedicated DQS routing resource. The DQS signal also feeds polarity control logic, which controls the polarity of
the clock to the sync registers in the input register blocks. Figure 2-35 and Figure 2-36 show how the DQS transi-
tion signals are routed to the PIOs.
The temperature, voltage and process variations of the DQS delay block are compensated by a set of calibration
(6-bit bus) signals from two dedicated DLLs (DDR_DLL) on opposite sides of the device. Each DLL compensates
DQS delays in its half of the device as shown in Figure 2-35. The DLL loop is compensated for temperature, volt-
age and process variations by the system clock and feedback loop.
DQS
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
PIO A
PIO B
2-37
Buffer
Delay
sysIO
LatticeECP2/M Family Data Sheet
PADA "T"
PADA "T"
PADA "T"
PADA "T"
PADA "T"
PADA "T"
PADA "T"
PADA "T"
PADB "C"
PADB "C"
PADB "C"
PADB "C"
PADB "C"
PADB "C"
PADB "C"
PADB "C"
DQS Pin
Assigned
PADA "T"
PADB "C"
LVDS Pair
LVDS Pair
LVDS Pair
LVDS Pair
LVDS Pair
LVDS Pair
LVDS Pair
LVDS Pair
LVDS Pair
Architecture