Supported Use Cases
401
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
Configuring SDRAM Timing Registers (SDTIMR1 and SDTIMR2)
The SDRAM timing register 1 (SDTIMR1) and SDRAM timing register 2 (SDTIMR2) configure the
DDR2/mDDR memory controller to meet the data sheet timing parameters of the attached memory device.
Each field in SDTIMR1 and SDTIMR2 corresponds to a timing parameter in the DDR2/mDDR data sheet
specification.
and
display the register field name and corresponding DDR2 data
sheet parameter name along with the data sheet value. These tables also provide a formula to calculate
the register field value and displays the resulting calculation. Each of the equations include a minus 1
because the register fields are defined in terms of DDR2/mDDR clock cycles minus 1. See
and
for more information.
(1)
The formula for the T_RRD field applies only for 8 bank DDR2/mDDR memories; when interfacing to DDR2/mDDR memories
with less than 8 banks, the T_RRD field should be calculated using the following formula: (t
RRD
× f
DDR2/mDDR_CLK
) - 1.
Table 14-18. SDTIMR1 Configuration
Register
Field Name
DDR2 Data
Manual
Parameter
Name
Description
Data Manual
Value (nS)
Formula
(Register field must be
≥
)
Register
Value
T_RFC
t
RFC
Refresh cycle time
127.5
(t
RFC
× f
DDR2/mDDR_CLK
) - 1
19
T_RP
t
RP
Precharge command to
refresh or activate
command
15
(t
RP
× f
DDR2/mDDR_CLK
) - 1
2
T_RCD
t
RCD
Activate command to
read/write command
15
(t
RCD
× f
DDR2/mDDR_CLK
) - 1
2
T_WR
t
WR
Write recovery time
15
(t
WR
× f
DDR2/mDDR_CLK
) - 1
2
T_RAS
t
RAS
Active to precharge
command
40
(t
RAC
× f
DDR2/mDDR_CLK
) - 1
5
T_RC
t
RC
Activate to Activate
command in the same
bank
55
(t
RC
× f
DDR2/mDDR_CLK
) - 1
8
T_RRD
(1)
t
RRD
Activate to Activate
command in a different
bank
10
((4 × t
RRD
) + (2 × t
CK
))/(4 × t
CK
) - 1
1
T_WTR
t
WTR
Write to read command
delay
10
(t
WTR
× f
DDR2/mDDR_CLK
) - 1
1
Table 14-19. SDTIMR2 Configuration
Register
Field Name
DDR2 Data
Manual
Parameter
Name
Description
Data Manual
Value
Formula
(Register field must be
≥
)
Register
Value
T_RASMAX
t
RAS
(MAX)
Active to precharge
command
70
μ
s
t
RAS
(MAX)/
DDR refresh rate
- 1
8
T_XP
t
XP
Exit power down to a non-
read command
2(t
CK
cycles)
If t
XP
> t
CKE
,
then T_XP = t
XP
- 1,
else T_XP = t
CKE
- 1
2
T_XSNR
t
XSNR
Exit self refresh to a non-
read command
137.5 nS
(t
XSNR
× f
DDR2/mDDR_CLK
) - 1
18
T_XSRD
t
XSRD
Exit self refresh to a read
command
200 (t
CK
cycles)
t
XSRD
- 1
199
T_RTP
t
RTP
Read to precharge
command delay
15 nS
(t
RTP
× f
DDR2/mDDR_CLK
) - 1
1
T_CKE
t
CKE
CKE minimum pulse width
3 (t
CK
cycles)
t
CKE
- 1
2