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Registers
409
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
14.4.4 SDRAM Timing Register 1 (SDTIMR1)
The SDRAM timing register 1 (SDTIMR1) configures the DDR2/mDDR memory controller to meet many of
the AC timing specification of the DDR2/mDDR memory. The SDTIMR1 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 memory data sheet for information on the
appropriate values to program each field. The SDTIMR1 is shown in
and described in
.
Figure 14-23. SDRAM Timing Register 1 (SDTIMR1)
31
25
24
22
21
19
18
16
T_RFC
T_RP
T_RCD
T_WR
R/W-Fh
R/W-2h
R/W-2h
R/W-2h
15
11
10
6
5
3
2
1
0
T_RAS
T_RC
T_RRD
Rsvd
T_WTR
R/W-6h
R/W-9h
R/W-1
R-0
R/W-1
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 14-26. SDRAM Timing Register 1 (SDTIMR1) Field Descriptions
Bit
Field
Value
Description
31-25
T_RFC
0-7Fh
Specifies the minimum number of DDR_CLK cycles from a refresh or load mode command to a refresh
or activate command, minus 1. Corresponds to the t
rfc
AC timing parameter in the DDR2/mDDR data
sheet. Calculate by:
T_RFC = (t
rfc
/DDR_CLK) - 1
24-22
T_RP
0-7h
Specifies the minimum number of DDR_CLK cycles from a precharge command to a refresh or activate
command, minus 1. Corresponds to the t
rp
AC timing parameter in the DDR2/mDDR data sheet.
Calculate by:
T_RP = (t
rp
/DDR_CLK) - 1
21-19
T_RCD
0-7h
Specifies the minimum number of DDR_CLK cycles from an activate command to a read or write
command, minus 1. Corresponds to the t
rcd
AC timing parameter in the DDR2/mDDR data sheet.
Calculate by:
T_RCD = (t
rcd
/DDR_CLK) - 1
18-16
T_WR
0-7h
Specifies the minimum number of DDR_CLK cycles from the last write transfer to a precharge
command, minus 1. Corresponds to the t
wr
AC timing parameter in the DDR2/mDDR data sheet.
Calculate by:
T_WR = (t
wr
/DDR_CLK) - 1
When the value of this field is changed from its previous value, the initialization sequence will begin.
15-11
T_RAS
0-1Fh
Specifies the minimum number of DDR_CLK cycles from an activate command to a precharge
command, minus 1. Corresponds to the t
ras
AC timing parameter in the DDR2/mDDR data sheet.
Calculate by:
T_RAS = (t
ras
/DDR_CLK) - 1
T_RAS must be greater than or equal to T_RCD.
10-6
T_RC
0-1Fh
Specifies the minimum number of DDR_CLK cycles from an activate command to an activate
command, minus 1. Corresponds to the t
rc
AC timing parameter in the DDR2/mDDR data sheet.
Calculate by:
T_RC = (t
rc
/DDR_CLK) - 1
5-3
T_RRD
0-7h
Specifies the minimum number of DDR_CLK cycles from an activate command to an activate command
in a different bank, minus 1. Corresponds to the t
rrd
AC timing parameter in the DDR2/mDDR data
sheet. Calculate by:
T_RRD = (t
rrd
/DDR_CLK) - 1
For an 8 bank DDR2/mDDR device, this field must be equal to ((4 × t
RRD
) + (2 × t
CK
)) / (4 × t
CK
) - 1.
2
Reserved
0
Reserved
1-0
T_WTR
0-3h
Specifies the minimum number of DDR_CLK cycles from the last write to a read command, minus 1.
Corresponds to the t
wtr
AC timing parameter in the DDR2/mDDR data sheet. Calculate by:
T_WTR = (t
wtr
/DDR_CLK) - 1