Cypress CY7C1345G - Manual (Page 6)

CY7C1345G
Document Number: 38-05517 Rev. *E Page 6 of 20
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
CO
) is 6.5 ns (133 MHz device).
The CY7C1345G supports secondary cache in systems using
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 use a linear burst
sequence. The burst order is user selectable and is determined
by sampling the MODE input. Accesses are 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 wrap
around 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:D]
) 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 (CE
1
, CE
2
, and CE
3
) and an
asynchronous Output Enable (OE) provide for easy bank
selection and output tri-state control. ADSP is ignored if CE
1
is
HIGH.
Single Read Accesses
A single read access is initiated when the following conditions
are satisfied at clock rise:
1. CE
1
, CE
2
, and CE
3
are all asserted active.
2. ADSP or ADSC is asserted LOW (if the access is initiated by
ADSC, the write inputs are deasserted during this first cycle).
The address presented to the address inputs is latched into the
address register and the burst counter or control logic and
presented to the memory core. If the OE input is asserted LOW,
the requested data is available at the data outputs a maximum
to t
CDV
after clock rise. ADSP is ignored if CE
1
is HIGH.
Single Write Accesses Initiated by ADSP
Single write access is initiated when the following conditions are
satisfied at clock rise:
1. CE
1
, CE
2
, and CE
3
are all asserted active
2. ADSP is asserted LOW.
The addresses presented are loaded into the address register
and the burst inputs (GW, BWE, and BW
x
) 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 is latched and
written into the device. Byte writes are allowed. During byte
writes, BW
A
controls DQ
A
and BW
B
controls DQ
B
, BW
C
controls
DQ
C
, and BW
D
controls DQ
D
. All IOs are tri-stated during a byte
write. Since this is a common IO device, the asynchronous OE
input signal is deasserted and the IOs are tri-stated prior to the
presentation of data to DQ
s
. As a safety precaution, the data
lines are tri-stated once a write cycle is detected, regardless of
the state of OE.
Single Write Accesses Initiated by ADSC
This write access is initiated when the following conditions are
satisfied at clock rise:
1. CE
1
, CE
2
, and CE
3
are all asserted active.
2. ADSC is asserted LOW.
3. ADSP is deasserted HIGH
4. The write input signals (GW, BWE, and BW
x
) indicate a write
access. ADSC is ignored if ADSP is active LOW.
The addresses presented are loaded into the address register
and the burst counter or control logic and delivered to the
memory core. The information presented to DQ
[D:A]
is written
into the specified address location. Byte writes are allowed.
During byte writes, BW
A
controls DQ
A
, BW
B
controls DQ
B
, BW
C
controls DQ
C
, and BW
D
controls DQ
D
. All IOs and even a byte
write are tri-stated when a write is detected. Since this is a
common IO device, the asynchronous OE input signal is
deasserted and the IOs are tri-stated prior to the presentation of
data to DQs. As a safety precaution, the data lines are tri-stated
once a write cycle is detected, regardless of the state of OE.
MODE Input
Static
Selects Burst Order. When tied to GND selects linear burst sequence. When tied to V
DD
or left
floating selects interleaved burst sequence. This is a strap pin and must remain static during device
operation. Mode Pin has an internal pull up.
NC No Connects. Not Internally connected to the die.
NC/9M,
NC/18M,
NC/36M
NC/72M,
NC/144M,
NC/288M,
NC/576M,
NC/1G
– No Connects. Not internally connected to the die. NC/9M, NC/18M, NC/36M, NC/72M, NC/144M,
NC/288M, NC/576M, and NC/1G are address expansion pins and are not internally connected to the
die.
Pin Definitions
(continued)
Name IO Description