Zynq-7000 AP SoC and 7 Series FPGAs MIS v4.1 213
UG586 November 30, 2016
www.xilinx.com
Chapter 1: DDR3 and DDR2 SDRAM Memory Interface Solution
Information on Sharing BUFG Clock (phy_clk)
The MIG 7 series DDR3 design includes an MMCM which outputs the phy_clk on a BUFG
route. It is not possible to share this clock amongst multiple controllers to synchronize the
user interfaces. This is not allowed because the timing from the FPGA logic to the PHY
Control block must be controlled. This is not possible when the clock is shared amongst
multiple controllers. The only option for synchronizing user interfaces amongst multiple
controllers is to create an asynchronous FIFO for clock domain transfer.
Information on Sync_Pulse
The MIG 7 series DDR3/DDR2 design includes one PLL that generates the necessary design
clocks. One of these outputs is the sync_pulse. The sync pulse clock is 1/16 of the
mem_refclk frequency and must have a duty cycle distortion of 1/16 or 6.25%. This clock
is distributed across the low skew clock backbone and keeps all PHASER_IN/_OUT and
PHY_Control blocks in sync with each other. The signal is sampled by the mem_refclk in
both the PHASER_INs/_OUTs and PHY_Control blocks. The phase, frequency, and duty cycle
of the sync_pulse is chosen to provide the greatest setup and hold margin across PVT.
DDR3 Pinout Examples
Table 1-69 shows an example of a 16-bit DDR3 interface contained within one bank. This
example is for a component interface using a 1 Gb x16 part. If x8 components are used or
a higher density part is needed that would require more address pins, these options are
possible:
• An additional bank can be used.
• RESET_N can be moved to another bank as long as timing is met. External timing for
this signal is not critical and a level shifter can be used.
• DCI cascade can be used to free up the VRN/VRP pins if another bank is available for
the DCI master.
Internal V
REF
is used in this example.
Table 1-69: 16-Bit DDR3 Interface Contained in One Bank
Bank Signal Name Byte Group I/O Type I/O Number
Special
Designation
1VRP – SE 49 –
1DQ15 D_11 P 48 –
1DQ14 D_10 N 47 –
1DQ13 D_09 P 46 –
1DQ12 D_08 N 45 –
1 DQS1_P D_07 P 44 DQS-P
To Next Page
Loading...
Need help?
General
