AS4C16M16S
Table 3. Pin Details
Symbol
Type
Description
CLK
Input
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.
CKE
Input
Clock Enable: CKE activates (HIGH) and deactivates (LOW) the CLK signal. If CKE
goes low synchronously with clock (set-up and hold time same as other inputs), the
internal clock is suspended from the next clock cycle and the state of output and burst
address is frozen as long as the CKE remains low. When all banks are in the idle state,
deactivating the clock controls the entry to the Power Down and Self Refresh modes.
CKE is synchronous except after the device enters Power Down and Self Refresh
modes, where CKE becomes asynchronous until exiting the same mode. The input
buffers, including CLK, are disabled during Power Down and Self Refresh modes,
providing low standby power.
BA0,BA1
Input
Bank Activate: BA0, BA1 input select the bank for operation.
BA1
0
BA0
0
Select Bank
BANK #A
BANK #B
BANK #C
BANK #D
0
1
1
0
1
1
A0-A12
Input
Address Inputs: A0-A12 are sampled during the BankActivate command (row address
A0-A12) and Read/Write command (column address A0-A8 with A10 defining Auto
Precharge) to select one location out of the 4M available in the respective bank. During
a Precharge command, A10 is sampled to determine if all banks are to be precharged
(A10 = HIGH). The address inputs also provide the op-code during a Mode Register Set
command.
CS#
Input
Input
Chip Select: CS# enables (sampled LOW) and disables (sampled HIGH) the command
decoder. All commands are masked when CS# is sampled HIGH. CS# provides for
external bank selection on systems with multiple banks. It is considered part of the
command code.
RAS#
Row Address Strobe: The RAS# signal defines the operation commands in
conjunction with the CAS# and WE# signals and is latched at the positive edges of
CLK. When RAS# and CS# are asserted "LOW" and CAS# is asserted "HIGH," either
the BankActivate command or the Precharge command is selected by the WE# signal.
When the WE# is asserted "HIGH," the BankActivate command is selected and the
bank designated by BA is turned on to the active state. When the WE# is asserted
"LOW," the Precharge command is selected and the bank designated by BA is switched
to the idle state after the precharge operation.
CAS#
WE#
Input
Column Address Strobe: The CAS# signal defines the operation commands in
conjunction with the RAS# and WE# signals and is latched at the positive edges of
CLK. When RAS# is held "HIGH" and CS# is asserted "LOW," the column access is
started by asserting CAS# "LOW." Then, the Read or Write command is selected by
asserting WE# "LOW" or "HIGH."
Input
Input
Write Enable: The WE# signal defines the operation commands in conjunction with the
RAS# and CAS# signals and is latched at the positive edges of CLK. The WE# input is
used to select the BankActivate or Precharge command and Read or Write command.
LDQM,
UDQM
Data Input/Output Mask: Controls output buffers in read mode and masks
Input data in write mode.
DQ0-DQ15
Input /
Output
Data I/O: The DQ0-15 input and output data are synchronized with the positive edges
of CLK. The I/Os are maskabled during Reads and Writes.
Confidential
4
Rev. 3
Feb. /2014