Datasheet, Volume 1 67
Signal Description
6.2 Memory Reference and Compensation Signals

Table 6-3. Memory Channel B Signals

Signal Name Description Direction/
Buffer Type
SB_BS[2:0] Bank Select: These signals define which banks are selected within
each SDRAM rank. O
DDR3
SB_WE# Write Enable Control Signal: This signal is used with SB_RAS# and
SB_CAS# (along with SB_CS#) to define the SDRAM Commands. O
DDR3
SB_RAS# RAS Control Signal: This sign al is used with SB_C AS# and SB _WE#
(along with SB_CS#) to define the SRAM Commands. O
DDR3
SB_CAS# CAS Control Signal: This signal is used with SB_RAS# and SB_WE#
(along with SB_CS#) to define the SRAM Commands. O
DDR3
SB_DQS[8:0]
SB_DQS#[8:0]
Data Strobes: SB_DQS[8:0] and its complement signal group make
up a differential strobe pair. The data is captured at the crossing point
of SB_DQS[8:0] and its SB_DQS#[8:0] during read and write
transactions.
I/O
DDR3
SB_DQ[63:0] Data Bus: Channel B data signal interface to the SDRAM data bus. I/O
DDR3
SB_MA[15:0] Memory Address: These signals are used to provide the multiplexed
row and column address to the SDRAM. O
DDR3
SB_CK[3:0]
SB_CK#[3:0]
SDRAM Differential Clock: Channel B SDRAM Differential clock
signal pair. The crossing of the positive edge of SB_CK and the
negative edge of its complement SB_CK# are used to sample the
command and control signals on the SDRAM.
O
DDR3
SB_CKE[3:0]
Clock Enable: (1 per rank) These signals are used to:
• Initialize the SDRAMs during power-up.
•Power down SDRAM ranks.
• Place all SDRAM ranks into and out of self-refresh during STR.
O
DDR3
SB_CS#[3:0] Chip Select: (1 per rank). These signals are used to select particular
SDRAM components during the active state. There is one Chip Select
for each SDRAM rank.
O
DDR3
SB_ODT[3:0] On Die Termination: Active Termination Control. O
DDR3

Table 6-4. Memory Reference and Compensation

Signal Name Description Direction/
Buffer Type
SM_VREF DDR3 Reference Voltage: This signal is used as a reference
voltage to the DDR3 controller. I
A
SA_DIMM_VREFDQ
SB_DIMM_VREFDQ
Memory Channel A/B DIMM DQ Voltage Reference: These
output pins are connected to the DIMMs, and are programmed to
have a reference voltage with optimized margin.
The nominal source impedance for these pins is 150
The step size is 7.7 mV for DDR3 (with no load).
O
A