CY7C1380CV25
CY7C1382CV25
PRELIMINARY
Document #: 38-05240 Rev. *A Page 8 of 33
Introduction
Functional Overview
All synchronous inpu ts pas s through i nput reg isters contro lled
by the rising edge of the clock. All data outputs pass through
output registers control led by the rising edge o f the clock. Maximum access delay from the clock rise (t
CO
) is 2.6 ns (250-MHz
device).
The CY7C1380CV25/CY7C1382CV25 supports secondary
cache in systems utilizing either a linear or interleaved burst
sequence. The interlea ved burst order s upports Pentiu m
®
and
i486 processors. The linear burst sequence is suited for processors that utiliz e a lin ear burst se quenc e. The b urst ord er is
user selecta ble , an d i s d etermined by sampli ng the MO DE i nput. Accesses can be initiated with either the Processor
Address Strobe (ADSP
) or the Controller Address Strobe
(ADSC
). Address advancement th rough the burs t sequence i s
controlled by the ADV
input. A two-bit on-chip wraparound
burst counter captures the first address in a burst sequence
and automatically increments the address for the rest of the
burst access.
Byte write operations are qualified with the Byte Write Enable
(BWE
) and Byte Write Select (BW
a,b,c,d
for CY7C1380V25 and
BW
a,b
for CY7C1382V25) inputs. A Gl obal Write Enab le (GW)
overrides all byte write input s and w rites data to all four by tes.
All writes are simplified with on-chip synchronous self-timed
write circuitry.
Synchronous Chip Select s (CE
1
, CE2, CE3 for TQFP / CE1 for
BGA) and an asynchronous Output Enable (OE
) provide for
easy bank selection and output three-state control. ADSP
is
ignored if CE
1
is HIGH.
Single Read Accesses
This access is initiated when the following conditions are satisfied at clock rise: (1) ADSP
or ADSC is asserted LOW, (2)
chip selects are all asserted active, and (3) the write signals
(GW
, BWE) are all deasserted HIGH. ADSP is ignored if CE
1
is HIGH. The address presented to the address inputs is
stored into the address advancement logic and the Address
Register while being presented to the memory core. The corresponding data is allowed to propagate to the input of the
Output Registers. At the risin g edge of the ne xt cloc k the dat a
is allowed to propagate through the output register and onto
the data bus within 2.6 ns (250-MHz device) if OE
is active
LOW. The only exception occurs when the SRAM is emerging
from a deselected state to a selected state, its outputs are
always three-stated during the first cycle of the access. After
the first cycle of the access, the outputs are controlled by the
OE
signal. Consecutive single read cycles are supported.
Once the SRAM is deselected at clock rise by the chip select
and either ADSP
or ADSC signals, its output will thr ee-state
immediately.
Single Write Accesses Initiated by ADSP
This access is initiated when both of the following conditions
are satisfied at clock rise: (1) ADSP
is asserted LOW, and (2)
chip select is asserted active. The address presented is loaded into the address register and the address advancement
logic while being deli vered to the RAM c ore. The wr ite signal s
(GW
, BWE, and BWx) and ADV inputs are ignored during this
first cycle.
ADSP
triggered write accesses require two clock cycles to
complete. If GW
is asserted LOW on the second clock rise, th e
data presented to the DQx inputs is written into the corresponding address location in the RAM core. If GW
is HIGH,
then the write operation is controlled by BWE
and BWx signals. The CY7C1380CV25/CY7C1382CV25 provides byte
write capabi li ty t h at i s de sc r ibe d i n th e wr ite c ycl e de s cri pt i on
table. Asserting the Byte Write Enable input (BWE
) with the
selected Byte Write (BWa,b,c,d for CY7C1380CV25 and
BW
a,b for CY7C1382CV25) input will selectively write to only
the desired bytes. Bytes not selec ted during a byte write op eration will remain unaltered. A synchronous self-timed write
mechanism has b een provided to simpli fy the write operatio ns.
Because the CY7C1380CV25/CY7C1382CV25 is a common
I/O device, the output enable (OE
) must be deasserted HIGH
before presenting data to the DQ
inputs. Doing so will threestate the output drivers. As a safety precaution, DQ are automatically three-stated whenever a write cycle is detected, regardless of the state of OE
.
Single Write Accesses Initiated by ADSC
ADSC write accesses are initiated when the following conditions are satisfied: (1) ADSC
is asserted LOW, (2) ADSP is
deasserted HIGH, (3) chip select is asserted active, and (4)
the appropriate combination of the write inputs (GW
, BWE,
and BW
x) are asserted active to con duct a write to the des ired
byte(s). ADSC
triggered write accesses require a single clock
cycle to complete. The address presented to A
[17:0]
is loaded
into the address register and the address advancement logic
while being delivered to the RAM core. The ADV
input is ig nored during this cycle. If a g lobal write is co nduct ed, the dat a
presented to the DQ[x:0] is written into the corresponding address location in the RAM core. If a byte write is conducted,
only the selected bytes are written. Bytes not selected during
a byte write operation will remain unaltered. A synchronous
self-timed write mechanism has been provided to simplify the
write operations.
Because the CY7C1380CV25/CY7C1382CV25 is a common
I/O device, the output enable (OE
) must be deasserted HIGH
before presenting data to the DQ[x:0] inputs. Doing so will
three-state the output drivers. As a saf ety pr ecauti on, DQ[x:0]
are automatically three-stated whenever a write cycle is detected, regardless of the state of OE
.
Burst Sequences
The CY7C1380CV25/CY7C1382CV25 provides a two-bit
wraparound counter, fed by A
[1:0]
, that implements either an
interleaved or linear burst s equence. The interle aved burst sequence is designed specifically to support Intel
®
Pentium applications. The linear burst sequence is designed to support
processors that follow a linear burst sequence. The burst sequence is user selectable through the MODE input.
Asserting ADV
LOW at clock rise will automa tic al ly increment
the burst counter to the next address in the burst sequence.
Both read and write burst operations are supported.