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
μs 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
μs 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
CC#
D
A
SRAM #2
R
P
S
#
W
P
S
#
B
W
S
#
ZQ
CQ/CQ#
Q
K#
CC#
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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