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AR# 34445 MIG v3.3 Virtex-6 DDR3 - ODT not asserted properly during initial write leveling and timing calibration causes calibration to fail

Description

MIG 3.3 and earlier Virtex-6 DDR3 designs may not properly assert ODT during initial write leveling and timing calibration. ODT timing following completion of calibration and initialization is correct. This issue will be seen as a failure to complete calibration (phy_init_done never goes high).

This issue only affects DDR3 designs using ODT where RTT_WR is OFF. This can be determined by looking at the top-level RTT_WR parameter. The Example Design top-level module is example_top.v/.vhd and the User Design top-level is core_name.v/.vhd.
RTT_WR = "OFF"

If this parameter is set to any other configuration, the design is not affected by this issue.

Solution

To work around this issue:

1. Open the phy_init.v module located in the MIG output 'rtl/phy' directory.

2. Locate the following code fragment in phy_init.v:

// Assert ODT when: (1) Write Leveling, (2) Issuing Write command
// Timing of ODT is not particularly precise (i.e. does not turn
// on right before write data, and turn off immediately after
// write is finished), but it doesn't have to be
generate
if (nSLOTS == 1) begin
always @(posedge clk)
if ((((RTT_NOM == "DISABLED") && (RTT_WR == "OFF")) ||
(wrlvl_done && !wrlvl_done_r)) && (DRAM_TYPE == "DDR3"))begin
phy_odt0 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
phy_odt1 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
end
else if ((((RTT_WR != "OFF") && (DRAM_TYPE == "DDR3"))
||((RTT_NOM != "DISABLED") && (DRAM_TYPE == "DDR2")))
&& ((wrlvl_odt) ||
(init_state_r == INIT_RDLVL_STG1_WRITE) ||
(init_state_r == INIT_RDLVL_STG1_WRITE_READ) ||
(init_state_r == INIT_RDLVL_STG2_WRITE) ||
(init_state_r == INIT_RDLVL_STG2_WRITE_READ))) begin
phy_odt0 <= #TCQ phy_tmp_odt0_r;
phy_odt1 <= #TCQ phy_tmp_odt1_r;
end else begin
phy_odt0 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
phy_odt1 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
end

3. Make the following change (highlighted in bold):
// Assert ODT when: (1) Write Leveling, (2) Issuing Write command
// Timing of ODT is not particularly precise (i.e. does not turn
// on right before write data, and turn off immediately after
// write is finished), but it doesn't have to be
generate
if (nSLOTS == 1) begin
always @(posedge clk)
if ((((RTT_NOM == "DISABLED") && (RTT_WR == "OFF")) ||
(wrlvl_done && !wrlvl_done_r)) && (DRAM_TYPE == "DDR3"))begin
phy_odt0 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
phy_odt1 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
end
else if (((DRAM_TYPE == "DDR3")
||((RTT_NOM != "DISABLED") && (DRAM_TYPE == "DDR2")))
&& ((wrlvl_odt) ||
(init_state_r == INIT_RDLVL_STG1_WRITE) ||
(init_state_r == INIT_RDLVL_STG1_WRITE_READ) ||
(init_state_r == INIT_RDLVL_STG2_WRITE) ||
(init_state_r == INIT_RDLVL_STG2_WRITE_READ))) begin
phy_odt0 <= #TCQ phy_tmp_odt0_r;
phy_odt1 <= #TCQ phy_tmp_odt1_r;
end else begin
phy_odt0 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
phy_odt1 <= #TCQ {CS_WIDTH*nCS_PER_RANK{1'b0}};
end

This issue will be resolved in MIG v3.4 which will be released with ISE 12.1 software.

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
33706 MIG v3.3 - Release Notes and Known Issues for ISE Design Suite 11.4 N/A N/A

Actions

AR# 34445
Date Created 02/19/2010
Last Updated 05/22/2012
Status Active
Type Known Issues
Devices
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