Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
595
DDR SDRAM Memory Controller—Intel
®
81341 and 81342
10. After waiting T
mrd
cycles, software issues a
mode-register-set
command by writing
one of the following options to SDIR to program DDR SDRAM parameters and to
Reset
DLL:
— 0002_9900H for CAS Latency = 3 and Write Recovery = 3, or
— 0003_9900H for CAS Latency = 3 and Write Recovery = 4, or
— 0002_A100H for CAS Latency = 4 and Write Recovery = 3, or
— 0003_A100H for CAS Latency = 4 and Write Recovery = 4, or
— 0002_A900H for CAS Latency = 5 and Write Recovery = 3, or
— 0003_A900H for CAS Latency = 5 and Write Recovery = 4
The DMCU supports the following DDR SDRAM mode parameters:
a. CAS Latency (tCAS) = 3, 4, or 5 for DDR2 based on the programmed setting in
. Note, when ODT is enabled CAS Latency must be => 4.
b. Burst Type = Sequential
c. Burst Length (BL) = four
11. After waiting T
mrd
cycles, software issues a
precharge-all
command to the
DDR SDRAM interface by setting the SDIR to 0002_0020H.
12. After waiting T
rp
cycles, software provides two
auto-refresh
cycles, accomplished
by setting SDIR to 0000_0010H, then ensure at least T
rfc
cycles between each
auto-refresh
command.
13. After the second
auto-refresh
cycle, software must wait T
rfc
cycles. Then,
software issues a
mode-register-set
command by writing one of the following
options to the SDIR to program DDR SDRAM parameters
without
resetting DLL:
— 0002_1900H for CAS Latency = 3 and Write Recovery = 3, or
— 0003_1900H for CAS Latency = 3 and Write Recovery = 4, or
— 0002_2100H for CAS Latency = 4 and Write Recovery = 3, or
— 0003_2100H for CAS Latency = 4 and Write Recovery = 4, or
— 0002_2900H for CAS Latency = 5 and Write Recovery = 3, or
— 0003_2900H for CAS Latency = 5 and Write Recovery = 4
14. DMCU may issue a
row-activate
command T
mrd
cycles after
mode-register-set
command.
15. Software re-enables the refresh counter by setting the RFR to the required value.
Figure 87. Supported DDR SDRAM Mode Register Settings
0
0
0
CAS Latency:
010: 2 (DDR only)
011: 3 (DDR2 only)
100: 4 (DDR2 only)
110: 2.5 (DDR only)
Other: X
Burst Type:
0: Sequential
Burst Length:
010: 4
A0
A12
Note: BA[1:0] must be 00
2
to select the Mode Register.
Operating Mode (A8:A7):
00: Normal Operation (Do not Reset DLL)
10: Normal Operation (In DLL Reset)
Other: X
A3
A6
0
The DDR SDRAM mode
register resides in the
DDR SDRAM devices.
B6261-01