CY7C1510KV18, CY7C1525KV18
CY7C1512KV18, CY7C1514KV18
Document Number: 001-00436 Rev. *E
Page 9 of 30
Echo Clocks
Echo clocks are provided on the QDR-II to simplify data capture
on high speed systems. Two echo clocks are generated by the
QDR-II. CQ is referenced with respect to C and CQ is referenced
with respect to C. These are free running clocks and are synchro-
nized to the output clock of the QDR-II. In the single clock mode,
CQ is generated with respect to K and CQ is generated with
respect to K. The timing for the echo clocks is shown in
Switching
Characteristics
on page 23.
PLL
These chips use a PLL that is designed to function between
120 MHz and the specified maximum clock frequency. During
power up, when the DOFF is tied HIGH, the PLL is locked after
20
μ
s of stable clock. The PLL can also be reset by slowing or
stopping the input clocks K and K for a minimum of 30 ns.
However, it is not necessary to reset the PLL to lock to the
desired frequency. The PLL automatically locks 20
μ
s after a
stable clock is presented. The PLL may be disabled by applying
ground to the DOFF pin. When the PLL is turned off, the device
behaves in QDR-I mode (with one cycle latency and a longer
access time).
Application Example
Figure 1
shows two QDR-II used in an application.
Figure 1. Application Example
R = 250
ohms
Vt
R
R = 250
ohms
Vt
Vt
R
Vt = Vddq/2
R = 50
ohms
R
C C#
D
A
SRAM #2
R
P
S
#
W
P
S
#
B
W
S
#
ZQ
CQ/CQ#
Q
K#
C C#
D
A
K
SRAM #1
R
P
S
#
W
P
S
#
B
W
S
#
ZQ
CQ/CQ#
Q
K#
BUS
MASTER
(CPU
or
ASIC)
DATA IN
DATA OUT
Address
RPS#
WPS#
BWS#
Source K
Source K#
Delayed K
Delayed K#
CLKIN/CLKIN#
K
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