CY7C1380CV25
CY7C1382CV25
PRELIMINARY
Document #: 38-05240 Rev. *A
Page 8 of 33
Introduction
Functional Overview
All synchronous inputs pass through input registers controlled
by the rising edge of the clock. All data outputs pass through
output registers controlled by the rising edge of the clock. Max-
imum access delay from the clock rise (tCO) is 2.6 ns (250-MHz
device).
The CY7C1380CV25/CY7C1382CV25 supports secondary
cache in systems utilizing either a linear or interleaved burst
sequence. The interleaved burst order supports Pentium® and
i486 processors. The linear burst sequence is suited for pro-
cessors that utilize a linear burst sequence. The burst order is
user selectable, and is determined by sampling the MODE in-
put. Accesses can be initiated with either the Processor
Address Strobe (ADSP) or the Controller Address Strobe
(ADSC). Address advancement through the burst sequence is
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 (BWa,b,c,d for CY7C1380V25 and
BWa,b for CY7C1382V25) inputs. A Global Write Enable (GW)
overrides all byte write inputs and writes data to all four bytes.
All writes are simplified with on-chip synchronous self-timed
write circuitry.
Synchronous Chip Selects (CE1, 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 CE1 is HIGH.
Single Read Accesses
This access is initiated when the following conditions are sat-
isfied 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 CE1
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 cor-
responding data is allowed to propagate to the input of the
Output Registers. At the rising edge of the next clock the data
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 three-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 load-
ed into the address register and the address advancement
logic while being delivered to the RAM core. The write signals
(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, the
data presented to the DQx inputs is written into the corre-
sponding address location in the RAM core. If GW is HIGH,
then the write operation is controlled by BWE and BWx sig-
nals. The CY7C1380CV25/CY7C1382CV25 provides byte
write capability that is described in the write cycle description
table. Asserting the Byte Write Enable input (BWE) with the
selected Byte Write (BWa,b,c,d for CY7C1380CV25 and
BWa,b for CY7C1382CV25) input will selectively write to only
the desired bytes. Bytes not selected during a byte write oper-
ation 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 inputs. Doing so will three-
state the output drivers. As a safety precaution, DQ are auto-
matically three-stated whenever a write cycle is detected, re-
gardless of the state of OE.
Single Write Accesses Initiated by ADSC
ADSC write accesses are initiated when the following condi-
tions 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 BWx) are asserted active to conduct a write to the desired
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 global write is conducted, the data
presented to the DQ[x:0] is written into the corresponding ad-
dress 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 safety precaution, DQ[x:0]
are automatically three-stated whenever a write cycle is de-
tected, 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 sequence. The interleaved burst se-
quence is designed specifically to support Intel® Pentium ap-
plications. The linear burst sequence is designed to support
processors that follow a linear burst sequence. The burst se-
quence is user selectable through the MODE input.
Asserting ADV LOW at clock rise will automatically increment
the burst counter to the next address in the burst sequence.
Both read and write burst operations are supported.
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