Registers
410
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
14.4.5 SDRAM Timing Register 2 (SDTIMR2)
Like the SDRAM timing register 1 (SDTIMR1), the SDRAM timing register 2 (SDTIMR2) also configures
the DDR2/mDDR memory controller to meet the AC timing specification of the DDR2/mDDR memory. The
SDTIMR2 is programmable only when the TIMUNLOCK bit is set to 1 in the SDRAM configuration register
(SDCR). Note that DDR_CLK is equal to the period of the DDR_CLK signal. See the DDR2/mDDR data
sheet for information on the appropriate values to program each field. SDTIMR2 is shown in
and described in
Figure 14-24. SDRAM Timing Register 2 (SDTIMR2)
31
30
27
26
25
24
23
22
16
Rsvd
T_RASMAX
T_XP
T_ODT
T_XSNR
R-0
R/W-8h
R/W-2h
R/W-2h
R/W-32h
15
8
7
5
4
0
T_XSRD
T_RTP
T_CKE
R/W-A7h
R/W-1
R/W-2h
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 14-27. SDRAM Timing Register 2 (SDTIMR2) Field Descriptions
Bit
Field
Value
Description
31
Reserved
0
Any writes to these bit(s) must always have a value of 0.
30-27
T_RASMAX
0-Fh
Specifies the maximum number of refresh rate intervals from Activate to Precharge command.
Corresponds to the t
ras
AC timing parameter and the refresh rate in the DDR2/mDDR data sheet.
Calculate by:
T_RASMAX = (t
ras
max/refresh_rate) - 1
Round down to the nearest cycle.
26-25
T_XP
0-3h
Specifies the minimum number of DDR_CLK cycles from Power Down exit to any other command
except a read command, minus 1. Corresponds to the t
xp
or t
cke
AC timing parameter in the
DDR2/mDDR data sheet. This field must satisfy the greater of t
XP
or t
CKE
.
If t
xp
> t
cke
, then calculate by T_XP = t
xp
- 1
If t
xp
< t
cke
, then calculate by T_XP = t
cke
- 1
24-23
T_ODT
0-3h
Specifies the minimum number of DDR_CLK cycles from ODT enable to write data driven for DDR2
SDRAM. T_ODT must be equal to (CAS latency - tAOND -1). T_ODT must be less than CAS latency
minus 1. This feature is not supported because the DDR_ODT signal is not pinned out.
22-16
T_XSNR
0-7Fh
Specifies the minimum number of DDR_CLK cycles from a self_refresh exit to any other command
except a read command, minus 1. Corresponds to the t
xsnr
AC timing parameter in the DDR2/mDDR
data sheet. Calculate by:
T_XSNR = (t
xsnr
/DDR_CLK) - 1
15-8
T_XSRD
0-FFh
Specifies the minimum number of DDR_CLK cycles from a self_refresh exit to a read command, minus
1. Corresponds to the t
xsrd
AC timing parameter in the DDR2/mDDR data sheet. Calculate by:
T_XSRD = t
xsrd
- 1
7-5
T_RTP
0-7h
Specifies the minimum number of DDR_CLK cycles from a last read command to a precharge
command, minus 1. Corresponds to the t
rtp
AC timing parameter in the DDR2/mDDR data sheet.
Calculate by:
T_RTP = (t
rtp
/DDR_CLK) - 1
4-0
T_CKE
0-1Fh
Specifies the minimum number of DDR_CLK cycles between transitions on the DDR_CKE pin, minus 1.
Corresponds to the t
cke
AC timing parameter in the DDR2/mDDR data sheet. Calculate by:
T_CKE = t
cke
- 1