ep1s25 Altera Corporation, ep1s25 Datasheet - Page 105

• Manufacturer Part Number: ep1s25
• Description: Stratix Device Family Data Sheet
• Manufacturer: Altera Corporation

Figure 2–54. Dynamically Programmable Counters & Delays in Stratix Device Enhanced PLLs
Altera Corporation
July 2005
scandata
scanaclr
scanclk
f
REF
÷n
Counters and Clock
Delay Settings are
Programmable
f
Δt
PLL reconfiguration data is shifted into serial registers from the logic
array or external devices. The PLL input shift data uses a reference input
shift clock. Once the last bit of the serial chain is clocked in, the register
chain is synchronously loaded into the PLL configuration bits. The shift
circuitry also provides an asynchronous clear for the serial registers.
For more information on PLL reconfiguration, see AN 282: Implementing
PLL Reconfiguration in Stratix & Stratix GX Devices.
Programmable Bandwidth
You have advanced control of the PLL bandwidth using the
programmable control of the PLL loop characteristics, including loop
filter and charge pump. The PLL’s bandwidth is a measure of its ability to
track the input clock and jitter. A high-bandwidth PLL can quickly lock
onto a reference clock and react to any changes in the clock. It also will
allow a wide band of input jitter spectrum to pass to the output. A low-
bandwidth PLL will take longer to lock, but it will attenuate all high-
frequency jitter components. The Quartus II software can adjust PLL
characteristics to achieve the desired bandwidth. The programmable
PFD
÷m
Charge
Pump
Δt
Loop
Filter
VCO
Stratix Device Handbook, Volume 1
All Output Counters and
Clock Delay Settings can
be Programmed Dynamically
÷g
÷e
÷l
Stratix Architecture
Δt
Δt
Δt
2–91