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MT40A256M16GE-075EAUT Datasheet, PDF (116/359 Pages) Micron Technology – Automotive DDR4 SDRAM
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4Gb: x8, x16 Automotive DDR4 SDRAM
VREFDQ Calibration
– "VVVVVV" are desired settings for VREFDQ.
• Issue ACT/WR/RD looking for pass/fail to determine VCENT (midpoint) as needed.
• To exit VREFDQ calibration, the last two VREFDQ calibration MR commands are:
– MR6[7:6]10 [5:0]VVVVVV* where VVVVVV* = desired value for V REFDQ.
– MR6[7]0 [6:0]XXXXXXX to exit VREFDQ calibration mode.
The following are typical script when applying the above rules for VREFDQ calibration
routine when performing VREFDQ calibration in Range 2:
• MR6[7:6]11 [5:0]XXXXXXX.
– Subsequent legal commands while in VREFDQ calibration mode: ACT, WR, WRA, RD,
RDA, PRE, DES, and MRS (to set VREFDQ values and exit VREFDQ calibration mode).
• All subsequent VREFDQ calibration MR setting commands are MR6[7:6]11
[5:0]VVVVVV.
– "VVVVVV" are desired settings for VREFDQ.
• Issue ACT/WR/RD looking for pass/fail to determine VCENT (midpoint) as needed.
• To exit VREFDQ calibration, the last two VREFDQ calibration MR commands are:
– MR6[7:6]11 [5:0]VVVVVV* where VVVVVV* = desired value for V REFDQ.
– MR6[7]0 [6:0]XXXXXXX to exit VREFDQ calibration mode.
Note:
Range may only be set or changed when entering VREFDQ calibration mode;
changing range while in or exiting VREFDQ calibration mode is illegal.
Figure 62: VREFDQ Training Mode Entry and Exit Timing Diagram
T0
CK_c
CK_t
T1
Ta0
Ta1
Tb0
Tb1
Tc0
Tc1
Td0
Td1
Td2
Command
DES
MRS
DES
CMD
DES
CMD
DES
MRS1,2
DES
WR
DES
tVREFDQE
tVREFDQX
VREFDQ training on
New VREFDQ
value or write
New VREFDQ
value or write
VREFDQ training off
Don’t Care
Notes:
1. New VREFDQ values are not allowed with an MRS command during calibration mode en-
try.
2. Depending on the step size of the latest programmed VREF value, VREF must be satisfied
before disabling VREFDQ training mode.
CCMTD-1725822587-10418
4gb_auto_ddr4_sdram_z90b.pdf - Rev. D 01/17 EN
116
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