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AR# 63463

MIG 7 Series DDR3 - Calibration updates to improve read and write margin result in an increase in calibration time starting with MIG v2.1 (Vivado 2014.2). Is there a way to reduce the calibration time?

Description

Calibration improvements were made in MIG v2.1 and v2.3 that improved read and write margin.

With these changes, the time for calibration to complete increased. 

What options are available to reduce the calibration time?

Solution

Background:


High read/write sample counts used in the 2014.2 to 2014.4 releases of MIG cause the increase in calibration time.  

Examples of calibration times across releases are shown below. 

To reduce the calibration time, Xilinx has performed hardware validation with reduced sample counts.  

The reduced sample counts will be included in the Vivado 2015.1 release of MIG.  

Until this version is available, a manual work-around is provided below.

Manual Changes to Reduce Calibration Time in MIG v2.3

1. Open the 'user_design/rtl/phy/mig_7series_v2_3_ddr_calib_top.v' module.  

Reduce the OCAL sample counts as shown below.

localparam SAMPLES = (SIM_CAL_OPTION=="NONE") ? 512 : 4; //original value of 2048
 
localparam OCAL_SIMPLE_SCAN_SAMPS = (SIM_CAL_OPTION=="NONE") ? 512 : 1; //original value of 2048

2. Open the 'user_design/rtl/phy/mig_7series_v2_3_ddr_phy_prbs_rdlvl.v' module. 

Reduce the loop count for complex read leveling as shown below.

localparam [11:0] NUM_SAMPLES_CNT  = (SIM_CAL_OPTION == "NONE") ? 'd12 : 12'h001; //original value of 50

3. Manually synthesize the MIG IP.  

Out of Context flow (OOC) cannot be used after modifying the IP rtl.

Note: Example files that include these changes are attached to this answer record.

Summary of Calibration Times

Release

Cal time at 400 MHz (4:1)

Cal time at 800 MHz (4:1)

 

32-bit

72-bit

32-bit

72-bit

2014.1

less than 1 sec

less than 1 sec

less than 1 sec

less than 1 sec

2014.3

less than 1 sec

~1 sec

less than 1 sec

little over 1 sec

2014.4

less than 4 sec

~7 sec

less than 2 sec

less than 4 sec

Reduced samp count

~1 sec

~2 sec

less than 1 sec

~1 sec


Note: The same number of reads and writes are performed for all MIG DDR3 configurations. 

Therefore, as the interface width widens and/or the datarate decreases, the time to complete these reads/writes increases causing longer calibration times.

Related Answer Records:
 
(Xilinx Answer 62368) Design Advisory for MIG 7 Series DDR3 - Calibration updates in MIG 7 Series v2.3 available with Vivado 2014.4 provide additional write margin
(Xilinx Answer 60687) MIG 7 Series DDR3 - Calibration updates available in MIG 7 Series v2.1 released with Vivado 2014.2 that provide additional read margin for data rates above 1333Mbps

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AR# 63463
Date Created 01/29/2015
Last Updated 02/13/2015
Status Active
Type General Article
Devices
  • Kintex-7
  • Artix-7
  • Virtex-7
IP
  • MIG 7 Series