
Signal Description
26
Intel
82845G/82845GL/82845GV GMCH Datasheet
2.2.2
SDR SDRAM Interface
The SDR interface signals are multiplexed with the DDR signals. At power up the functional strap
setting on MEMSEL determines whether the memory interface is set up for DDR or SDR. The
DDR-to-SDR signal mapping is provided in
Table 2-1
.
Signal Name
Type
Description
SCK_[7:0]
O LVTTL
SDR System Memory Clock:
These signals provide the 133 MHz SDRAM
clocks for the DIMMs. Note that there are two SCK per SDRAM row.
SCS_[7:0]#
O
LVTTL
Chip Select:
These pins select the particular SDRAM components during the
active state. Note that there are two SCS# per SDRAM row. These signals can
be toggled on every rising system memory clock edge.
SMAA_[12:0]
O
LVTTL
Memory Address:
These signals provide the multiplexed row and column
address to SDRAM.
SBA_[1:0]
O
LVTTL
Bank Select (Bank Address):
The bank select signals and memory address
signals combine to address every possible location within an SDRAM device.
SRAS#
O
LVTTL
Row Address Strobe:
SRAS# is used with SCAS# and SWE# (along with
SCS#) to define the SDRAM commands.
SCAS#
O
LVTTL
Column Address Strobe:
SCAS# is used with SRAS# and SWE# (along with
SCS#) to define the SDRAM commands.
SWE#
O
LVTTL
Write Enable:
SWE# is used with SCAS# and SRAS# (along with SCS#) to
define the SDRAM commands.
SDQ_[63:0]
I/O
LVTTL
Data Lines:
SDQ_[63:0] interface to the SDRAM data bus.
SDM_[7:0]
O LVTTL
Data Mask:
When activated during writes, the corresponding data groups in the
SDRAM are masked. There is one SDM for every eight data lines.
SCKE_[3:0]
O
LVTTL
Clock Enable:
These signals are used for placing all SDRAM rows into and out
of self-refresh during Suspend-to-RAM. SCKE is also used to dynamically
power down inactive SDRAM rows. There is one SCKE per SDRAM row.
SRDCLK_OUT
O
LVTTL
Read Clock Out:
Feedback testpoint signal used to emulate source-synch
clocking for reads. This pin should be connect to SRDCLK_IN through an
un-
populated
backside resistor site.
SRDCLK_IN
I
LVTTL
Read Clock Input:
Feedback testpoint signal used to emulate source-synch
clocking for reads.
Table 2-1. DDR-to-SDR Signal Mapping (Sheet 1 of 3)
DDR Ball Name
SDR Ball Name
Ball #
DDR Ball Name
SDR Ball Name
Ball #
SMXRCOMP
SMXRCOMP
AF10
SWE#
SCKE_3
AP29
SMYRCOMP
SMYRCOMP
AJ34
SDQ_5
SDQ_1
AP3
SDQ_59
SDQ_63
AJ36
SDQ_43
SDQ_54
AP30
SCKE_2
SWE#
AK14
SCS_1#
SCS_6#
AP31
SMAA_9
SCS_4#
AK16
SDQ_52
SDQ_24
AP32
SMAB_5
SCS_0#
AK18
SCMDCLK_5
SCMDCLK_2
AP33
SMAA_3
SMAA_0
AK20
SDQ_54
SDQ_57
AP34
SCMDCLK_0#
SMAA_5
AK22
SDQ_51
SDQ_27
AP35
SRCVEN_OUT#
SRCVEN_OUT#
AK24
SDQ_60
SDQ_59
AP36
SMAA_10
SBA_0
AK26
SDM_0
SDQ_2
AP4