AS7C33128PFS16B
AS7C33128PFS18B
®
10/29/03; v.1.0 Alliance Semiconductor P. 2 of 14
Functional description
The AS7C33128PFS16B and AS7C33128PFS18B are high performance CMOS 2 Mbit synchronous Static Random
Access Memory (SRAM) devices organized as 131,072 words × 16 or 18 bits and incorporate a pipeline for highest
frequency on any given technology.
Timing for this device is compatible with existing Pentium® synchronous cache specifications. This architecture is
suited for ASIC, DSP (TMS320C6X), and PowerPC™1-based systems in computing, datacom, instrumentation, and
telecommunications systems.
Fast cycle times of 5.0/6.0/7.5 ns with clock access times (tCD) of 3.0/3.5/4.0 ns enable 200, 166 and 133 MHz bus
frequencies. Three chip enable inputs permit easy memory expansion. Burst operation is initiated in one of two
ways: the controller address strobe (ADSC), or the processor address strobe (ADSP). The burst advance pin (ADV)
allows subsequent internally generated burst addresses.
Read cycles are initiated with ADSP (regardless of WE and ADSC) using the new external address clocked into the
on-chip address register. When ADSP is sampled LOW, the chip enables are sampled active, and the output buffer
is enabled with OE. In a read operation the data accessed by the current address, registered in the address registers
by the positive edge of CLK, are carried to the data-out registers and driven on the output pins on the next positive
edge of CLK. ADV is ignored on the clock edge that samples ADSP asserted but is sampled on all subsequent clock
edges. Address is incremented internally for the next access of the burst when ADV is sampled LOW and both
address strobes are HIGH. Burst mode is selectable with the
LBO
input. With
LBO
unconnected or driven HIGH,
burst operations use a Pentium® count sequence. With
LBO
driven LOW the device uses a linear count sequence
suitable for PowerPC™ and many other applications.
Write cycles are performed by disabling the output buffers with OE and asserting a write command. A global
write enable GWE writes all 16/18 bits regardless of the state of individual BW[a:b] inputs. Alternately, when
GWE is HIGH, one or more bytes may be written by asserting BWE and the appropriate individual byte BWn
signal(s).
BWn is ignored on the clock edge that samples ADSP LOW, but is sampled on all subsequent clock edges. Output
buffers are disabled when BWn is sampled LOW (regardless of OE). Data is clocked into the data input register
when BWn is sampled LOW. Address is incremented internally to the next burst address if BWn and ADV are
sampled LOW.
Read or write cycles may also be initiated with ADSC instead of ADSP. The differences between cycles initiated
with ADSC and ADSP follow.
ADSP must be sampled HIGH when ADSC is sampled LOW to initiate a cycle with ADSC.
WE
signals are sampled on the clock edge that samples ADSC LOW (and ADSP HIGH).
Master chip select CE0 blocks ADSP, but not ADSC.
The AS7C33128PFS16B and AS7C33128PFS18B operate from a 3.3V supply. I/Os use a separate power supply that
can operate at 2.5V or 3.3V. These devices are available in a 100-pin 14×20 mm TQFP packaging.
1. PowerPC™ is a trademark International Business Machines Corporation