Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
601
DDR SDRAM Memory Controller—Intel
®
81341 and 81342
7.3.3.8
DDR SDRAM Mode Programming
The DMCU programs the DDR SDRAM devices through a
mode-register-set
command.
During the initialization sequence this command sets the DDR SDRAM mode register
(see
Section 7.3.3.7, “DDR SDRAM Initialization” on page 594
) by programming the
SDIR and SDCR[1:0].
The DDR SDRAM state machine ensures that a
row-activate
command is issued no
sooner than T
mrd
cycles after the
mode-register-set
command.
The values to be programmed in the SDCR[1:0] registers are based on the SDRAM
devices being interfaced to 81341 and 81342. Because the parameters that define the
time between allowed commands are programmable, this allows flexibility in the type
of DDR device that is selected, in addition to de-coupling the hardware to any
frequency dependencies. See
Section 7.8.2, “SDRAM Control Register 0 — SDCR0” on
Section 7.8.3, “SDRAM Control Register 1 — SDCR1” on page 630
for
equations and values for programming of the MCU timing parameters.
Note:
The DMCU_DDRSM does NOT interact properly with the DDR SDRAM until the
SDCR[1:0]
registers
have been programmed.
Table 368. SDCR[1:0] Timing Parameters Summary
Parameter
Source
Use
Parameter
Source
Use
tBL
JEDEC
tRMW
SBSR[11:08]
tCAS
JEDEC
, and
SDCR0[10:08]
tRTW
SDCR1[22:19]
tEDP
81341 and
81342
SDCR0[18:16] tWDL
SDCR0[13:12]
tRAS
JEDEC
SDCR0[31:27] tWR
JEDEC
and
SDCR1[11:9]
tRC
JEDEC
SDCR1[08:04] tWTR
JEDEC
tRCD
JEDEC
SDCR0[22:20] tWTRD
SDCR1[3:0]
tRFC
JEDEC
SDCR1[17:12] tWTCMD
SDCR1[26:23]
tRP
JEDEC
SDCR0[26:24] tRTP
JEDEC
tRTCMD
SDCR1[30:27]