Zynq-7000 AP SoC and 7 Series FPGAs MIS v4.1
624
UG586 November 30, 2016
Chapter 4:
LPDDR2 SDRAM Memory Interface Solution
The parameters listed in
depend on the selected memory clock frequency,
memory device, memory configuration, and FPGA speed grade. The values for these
parameters are integrated in the
memc_ui_top
IP core and should not be modified in the
top-level.
RECOMMENDED:
Xilinx strongly recommends that the MIG tool be rerun for different configurations.
DIFF_TERM_REFCLK
“TRUE,” “FALSE”
Differential termination for IDELAY
reference clock input pins.
Notes:
1. The lower limit (maximum frequency) is pending characterization.
2. Core initialization during simulation can be greatly reduced by using SIM_BYPASS_INIT_CAL. Three simulation modes are
supported. Setting SIM_BYPASS_INIT_CAL to FAST causes write leveling and read calibration to occur on only one bit per
memory device. This is then used across the remaining data bits. Setting SIM_BYPASS_INIT_CAL to SIM_INIT_CAL_FULL causes
complete memory initialization and calibration sequence occurs on all byte groups. SIM_BYPASS_INIT_CAL should be set to
SIM_INIT_CAL_FULL for simulations only. SIM_BYPASS_INIT_CAL should be set to OFF for implementation, or the core does
not function properly.
3. When set to NORM or RELAXED, ORDERING enables the reordering algorithm in the Memory Controller. When set to STRICT,
request reordering is disabled, which might limit throughput to the external memory device. However, it can be helpful
during initial core integration because requests are processed in the order received; the user design does not need to keep
track of which requests are pending and which requests have been processed.
4. This parameter is prefixed with the module name entered in MIG during design generation. If the design is generated with
the module name as mig_7series_0, then IODELAY_GRP parameter name is mig_7series_0_IODELAY_MIG.
Table 4-25:
7 Series FPGA Memory Solution Configuration Parameters
(Cont’d)
Parameter
Description
Options
Table 4-26:
Embedded 7 Series FPGAs Memory Solution Configuration Parameters
Parameter
Description
Options
tFAW
This is the minimum interval of four active
commands.
This value, in picoseconds, is based
on the device selection in the MIG
tool.
tRRD
This is the ACTIVE-to-ACTIVE minimum
command period.
This value, in picoseconds, is based
on the device selection in the MIG
tool.
tRAS
This is the minimum ACTIVE-to-PRECHARGE
period for memory.
This value, in picoseconds, is based
on the device selection in the MIG
tool.
tRCD
This is the ACTIVE-to-READ or -WRITE
command delay.
This value, in picoseconds, is based
on the device selection in the MIG
tool.
tREFI
This is the average periodic refresh interval
for memory.
This value, in picoseconds, is based
on the device selection in the MIG
tool.
tRFC
This is the REFRESH-to-ACTIVE or
REFRESH-to-REFRESH command interval.
This value, in picoseconds, is based
on the device selection in the MIG
tool.