NAD T748 Service Manual page 27

Pin Descriptions
SYMBOL TYPE
CLK Input
CKE Input
/CS Input
/CAS,
/RAS, Input
/WE
DQML,
Input
DQMU
BA0, BA1 Input
A0–A11 Input
DQ0–DQ15 I/O
NC –
V Q Supply
DD
V Q Supply
SS
V Supply
DD
V Supply
SS
Clock: CLK is driven by the system clock. All SDRAM input signals are sampled on the positive
edge of CLK. CLK also increments the internal burst counter and controls the output registers.
Clock Enable: CKE activates (HIGH) and deactivates (LOW) the CLK signal. Deactivating the
clock provides PRECHARGE POWER-DOWN and SELF REFRESH operation (all banks idle),
ACTIVE POWER-DOWN (row active in any bank), DEEP POWER DOWN (all banks idle), or
CLOCK SUSPEND operation (burst/access in progress). CKE is synchronous except after the
device enters power-down and self refresh modes, where CKE becomes asynchronous until
after exiting the same mode. The input buffers, including CLK, are disabled during power-down
and self refresh modes, providing low standby power. CKE may be tied HIGH.
Chip Select: /CS enables (registered LOW) and disables (registered HIGH) the command
decoder. All commands are masked when /CS is registered HIGH. /CS provides for external
bank selection on systems with multiple banks. /CS is considered part of the command code.
Command Inputs: /CAS, /RAS, and /WE (along with /CS) define the command being entered.
Input/Output Mask: DQM is sampled HIGH and is an input mask signal for write accesses and an
output enable signal for read accesses. Input data is masked during a WRITE cycle. The output
buffers are placed in a High-Z state (two-clock latency) when during a READ cycle.
DQML corresponds to DQ0–DQ7, DQMU corresponds to DQ8–DQ15.
Bank Address Input(s): BA0 and BA1 define to which bank the ACTIVE, READ, WRITE or
PRECHARGE command is being applied. These pins also select between the mode register and
the extended mode register.
A0-11 specify the Row / Column Address in conjunction with BA0,1. The Row Address is
specified by A0-11. The Column Address is specified by A0-7. A10 is also used to indicate
precharge option. When A10 is high at a read / write command, an auto precharge is performed.
When A10 is high at a precharge command, all banks are precharged.
Data Input/Output: Data bus.
Internally Not Connected: These could be left unconnected, but it is recommended they be
connected or V .
SS
DQ Power: Provide isolated power to DQs for improved noise immunity.
DQ Ground: Provide isolated ground to DQs for improved noise immunity.
Core Power Supply.
Ground.
DESCRIPTION
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