AS4C8M16SA-AUTOMOTIVE Datasheet, PDF (5/55 Pages) Alliance Semiconductor Corporation – Auto Refresh and Self Refresh

AS4C8M16SA-Automotive
Pin Descriptions
Table 3. Pin Details
Symbol
CLK
CKE
BA0,BA1
Type
Input
Input
Input
Description
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. 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.
Bank Activate: BA0, BA1 input select the bank for operation.
A0-A11
CS#
RAS#
CAS#
WE#
Input
Input
Input
Input
Input
BA1
BA0
Select Bank
0
0
BANK #A
0
1
BANK #B
1
0
BANK #C
1
1
BANK #D
Address Inputs: A0-A11 are sampled during the BankActivate command (row
address A0-A11) and Read/Write command (column address A0-A8 with A10
defining Auto Precharge) to select one location out of the 2M 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.
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.
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.
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."
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.
Confidential
4
Rev. 2.0
Mar. /2015