CY7C1339B-166BGC Просмотр технического описания (PDF) - Cypress Semiconductor
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CY7C1339B-166BGC Datasheet PDF : 17 Pages
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CY7C1339B
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.
Maximum access delay from the clock rise (tCO) is 3.5 ns
(166-MHz device).
The CY7C1339B 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 processors
that utilize a linear burst sequence. The burst order is user
selectable, and is determined by sampling the MODE input.
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 (BW[3:0]) 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.
Three synchronous Chip Selects (CE1, CE2, CE3) 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
satisfied at clock rise: (1) ADSP or ADSC is asserted LOW, (2)
CE1, CE2, CE3 are all asserted active, and (3) the Write
signals (GW, BWE) are all deserted HIGH. ADSP is ignored if
CE1 is HIGH. The address presented to the address inputs
(A[16:0]) 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 rising edge of the next clock the
data is allowed to propagate through the output register and
onto the data bus within 3.5 ns (166-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) CE1, CE2, CE3 are all asserted active. The address
presented to A[16:0] is loaded into the address register and the
address advancement logic while being delivered to the RAM
core. The Write signals (GW, BWE, and BW[3:0]) 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 DQ[31:0] 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 BW[3:0]
signals. The CY7C1339B provides Byte Write capability that
is described in the Write Cycle Descriptions table. Asserting
the Byte Write Enable input (BWE) with the selected Byte
Write (BW[3:0]) input will selectively write to only the desired
bytes. 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 CY7C1339B is a common I/O device, the Output
Enable (OE) must be deserted HIGH before presenting data
to the DQ[31:0] inputs. Doing so will three-state the output
drivers. As a safety precaution, DQ[31:0] 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 condi-
tions are satisfied: (1) ADSC is asserted LOW, (2) ADSP is
deserted HIGH, (3) CE1, CE2, CE3 are all asserted active, and
(4) the appropriate combination of the Write inputs (GW, BWE,
and BW[3:0]) 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[16:0] is loaded into the address register and the address
advancement logic while being delivered to the RAM core. The
ADV input is ignored during this cycle. If a global Write is
conducted, the data presented to the DQ[31:0] 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 CY7C1339B is a common I/O device, the Output
Enable (OE) must be deserted HIGH before presenting data
to the DQ[31:0] inputs. Doing so will three-state the output
drivers. As a safety precaution, DQ[31:0] are automatically
three-stated whenever a Write cycle is detected, regardless of
the state of OE.
Burst Sequences
The CY7C1339B provides a two-bit wraparound counter, fed
by A[1:0], that implements either an interleaved or linear burst
sequence. The interleaved burst sequence is designed specif-
ically 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 automatically increment
the burst counter to the next address in the burst sequence.
Both Read and Write burst operations are supported.
Interleaved Burst Sequence
First
Address
A[1:0]
00
01
10
11
Second
Address
A[1:0]
01
00
11
10
Third
Address
A[1:0]
10
11
00
01
Fourth
Address
A[1:0]
11
10
01
00
Document #: 38-05141 Rev. *A
Page 5 of 17
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