IS42S32200B
FUNCTIONAL DESCRIPTION
The 64Mb SDRAMs 512K x 32 x 4 banks) are quad-bank
DRAMs which operate at 3.3V and include a synchronous
interface (all signals are registered on the positive edge of
the clock signal, CLK). Each of the 16,777,216-bit banks
is organized as 2,048 rows by 256 columns by 32bits.
Read and write accesses to the SDRAM are burst oriented;
accesses start at a selected location and continue for a
programmed number of locations in a programmed
sequence. Accesses begin with the registration of an
ACTIVE command which is then followed by a READ or
WRITE command. The address bits registered coincident
with the ACTIVE command are used to select the bank
and row to be accessed (BA0 and BA1 select the bank, A0-A10
select the row). The address bits (A0-A7) registered coincident
with the READ or WRITE command are used to select the
starting column location for the burst access.
Prior to normal operation, the SDRAM must be initialized.
The following sections provide detailed information covering
device initialization, register definition, command
descriptions and device operation.
ISSI
Initialization
®
SDRAMs must be powered up and initialized in a
predefined manner.
The 64M SDRAM is initialized after the power is applied
to V
DD
and V
DDQ
(simultaneously) and the clock is stable.
A 100µs delay is required prior to issuing any command
other than a COMMAND INHIBIT or a NOP. The COMMAND
INHIBIT or NOP may be applied during the 100us period
and continue should at least through the end of the period.
With at least one COMMAND INHIBIT or NOP command
having been applied, a PRECHARGE command should be
applied once the 100µs delay has been satisfied. All
banks must be precharged. This will leave all banks in an
idle idle state where two AUTO REFRESH cycles must be
performed. After the AUTO REFRESH cycles are complete,
the SRDRAM is then ready for mode register programming.
The mode register should be loaded prior to applying any
operational command because it will power up in an
unknown state.
Integrated Silicon Solution, Inc. — www.issi.com —
1-800-379-4774
Rev. 00C
09/29/03
11
ISSI [ INTEGRATED SILICON SOLUTION, INC ]
