CY7C1345B
4
Functional Overview
All synchronous inputs pass through input registers controlled
by the rising edge of the clock. Maximum access delay from
the clock rise (t CDV) is 7.5 ns (117-MHz device).
The CY7C1345B supports secondary cache in systems utiliz-
ing either a linear or interleaved burst sequence. The inter-
leaved 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 ad-
dress 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 synchro-
nous self-timed write circuitry.
Three synchronous Chip Selects (CE1, CE2, CE3) and an
asynchronous Output Enable (OE) provide for easy bank se-
lection and output three-state control. ADSP is ignored if CE1
is HIGH.
Single Read Accesses
A single read access is initiated when the following conditions
are satisfied at clock rise: (1) CE1, CE2, and CE3 are all as-
serted active, and (2) ADSP or ADSC is asserted LOW (if the
access is initiated by ADSC, the write inputs must be deassert-
ed during this first cycle). The address presented to the ad-
dress inputs is latched into the address register and the burst
counter/control logic and presented to the memory core. If the
OE input is asserted LOW, the requested data will be available
at the data outputs a maximum to tCDV after clock rise. ADSP
is ignored if CE1 is HIGH.
Functional Description
Single Write Accesses Initiated by ADSP
This access is initiated when the following conditions are sat-
isfied at clock rise: (1) CE1, CE2, and CE3 are all asserted
active, and (2) ADSP is asserted LOW. The addresses pre-
sented are loaded into the address register and the burst
counter/control logic and delivered to the RAM core. The write
inputs (GW, BWE, and BW[3:0]) are ignored during this first
clock cycle. If the write inputs are asserted active (see Write
Cycle Descriptions table for appropriate states that indicate a
write) on the next clock rise, the appropriate data will be
latched and written into the device. Byte writes are allowed.
During byte writes, BW0 controls DQ[7:0], BW1 controls
DQ[15:8], BW2 controls DQ[23:16], and BW3 controls DQ[31:24].
All I/Os are three-stated during a byte write. Since this is a
common I/O device, the asynchronous OE input signal must
be deasserted and the I/Os must be three-stated prior to the
presentation of data to DQ[31:0]. As a safety precaution, the
data lines are three-stated once a write cycle is detected, re-
gardless of the state of OE.
CE3
Input-
Synchronous
Chip Enable 3 Input, active LOW. Sampled on the rising edge of CLK. Used in conjunction with CE1
and CE2 to select/deselect the device.
OE
Input-
Asynchronous
Output Enable, asynchronous input, active LOW. Controls the direction of the I/O pins. When LOW,
the I/O pins behave as outputs. When deasserted HIGH, I/O pins are three-stated, and act as input
data pins.
ZZ
Input-
Asynchronous
Snooze Input. Active HIGH asynchronous. When HIGH, the device enters a low-power standby
mode in which all other inputs are ignored, but the data in the memory array is maintained.Leaving
ZZ floating or NC will default the device into an active state. ZZ pin has an internal pull-down.
MODE
-
Mode Input. Selects the burst order of the device. Tied HIGH selects the interleaved burst order.
Pulled LOW selects the linear burst order. When left floating or NC, defaults to interleaved burst
order. Mode pin has an internal pull-up.
DQ[31:0],
DP[3:0]
I/O-
Synchronous
Bidirectional Data I/O lines. As inputs, they feed into an on-chip data register that is triggered by
the rising edge of CLK. As outputs, they deliver the data contained in the memory location specified
by A[16:0] during the previous clock rise of the read cycle. The direction of the pins is controlled by
OE in conjunction with the internal control logic. When OE is asserted LOW, the pins behave as
outputs. When HIGH, DQ[31:0] and DP[3:0] are placed in a three-state condition. The outputs are
automatically three-stated when a Write cycle is detected.
VDD
Power Supply
Power supply inputs to the core of the device. Should be connected to 3.3V power supply.
VSS
Ground
Ground for the I/O circuitry of the device. Should be connected to ground of the system.
VSSQ
Ground
Ground for the device. Should be connected to ground of the system.
VDDQ
I/O Power
Supply
Power supply for the I/O circuitry. Should be connected to a 3.3V power supply.
NC
-
No connects.
DNU
-
Do not use pins. Should be left unconnected or tied LOW.
Pin Descriptions (continued)
Name
I/O
Description
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