Zynq-7000 AP SoC and 7 Series FPGAs MIS v4.1
120
UG586 November 30, 2016
Chapter 1:
DDR3 and DDR2 SDRAM Memory Interface Solution
• When HR banks are selected for memory interface pins in GUI and the memory
frequencies
≥
400 MHz, the phase is 337.5°.
• When HR banks are selected for memory interface pins in GUI and the memory
frequencies are between 200–400 MHz (excluding 400 MHz), the phase is 0°.
The default setting for the PLL multiply (M) and divide (D) values is for the system clock
input frequency to be equal to the memory clock frequency. This 1:1 ratio is not required.
The PLL input divider (D) can be any value listed in the
7 Series FPGAs Clocking Resources
User Guide
(UG472)
as long as the PLLE2 operating conditions are met and the
other constraints listed here are observed. The PLL multiply (M) value must be between 1
and 16 inclusive. The PLL output divider (O) for the memory clock must be 2 for 800 Mb/s
and above, and 4 for 400 to 800 Mb/s. The PLL VCO frequency range must be kept in the
range specified in the silicon data sheet. The sync_pulse must be 1/16 of the mem_refclk
frequency and must have a duty cycle of 1/16 or 6.25%. For information on physical
placement of the PLL and the System Clock CCIO input, see
The details of the ISERDES/OSERDES connectivity are shown in
and
.
Internal (FPGA) Logic Clock
The internal FPGA logic is clocked by a global clocking resource at a half or quarter
frequency of the DDR2 or DDR3 SDRAM clock frequency, which depends on 4:1 or 2:1 mode
selected in the MIG tool. This PLL also outputs the high-speed DDR2 or DDR3 memory
clock.
X-Ref Target - Figure 1-52
Figure 1-52:
Clocking Architecture
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P
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