Cypress CY25822-2 User Manual
Page 4
CY25822-2
Document #: 38-07531 Rev. **
Page 4 of 9
Bytes 2 through 5: Reserved Registers
PWRDWN# (Power-down) Clarification
The PWRDWN# (Power-down) pin is used to shut off ALL
clocks prior to shutting off power to the device. PWRDWN# is
an asynchronous active LOW input. This signal is synchro-
nized internally to the device powering down the clock synthe-
sizer. PWRDWN# is an asynchronous function for powering up
the system. When PWRDWN# is low, all clocks are driven to
a LOW value and held there and the VCO and PLLs are also
powered down. All clocks are shut down in a synchronous
manner so has not to cause glitches while transitioning to the
low ‘stopped’ state. When PWRDWN# is deasserted the
clocks should remain stopped until the VCO is stable and
within specification (t
STABLE
). A stopped clock is either
tri-stated or driven low depending on the state of the tri-state
enable I
2
C register bit. CY25822 clocks that are stopped in the
driven state are driven low.
The CLKIN input must be on and within specified operating
parameters before PWRDWN# is asserted and it must remain
in this state while PWRDWN# is asserted.
0
1
0
1
Down
2.0
0
1
1
0
Down
2.5
0
1
1
1
Down
3.0
1
0
0
0
Center
±0.3
1
0
0
1
Center
±0.4
1
0
1
0
Center
±0.5
1
0
1
1
Center
±0.6
1
1
0
0
Center
±0.8
1
1
0
1
Center
±1.0
1
1
1
0
Center
±1.25
1
1
1
1
Center
±1.5
Table 4. Spread Spectrum Select (continued)
SS3
SS2
SS1
SS0
Spread Mode
Spread Amount%
Byte 1: Control Register
Bit
@Pup
Pin#
Name
Pin Description
7
1
5
REFEN
REFOUT enable
0 = disabled, 1 = enabled
6
1
5
REFSLEW
REFOUT edge rate control
0 = slow, 1 = nominal
5
0
Not Applicable
Reserved.
4
0
Not Applicable
Reserved
3
1
4
CLKSLEW
CLKOUT edge rate control
0 = slow, 1 = nominal
2
1
4
CLKEN
CLKOUT enable
0 =disabled, 1 = enabled
1
0
Not Applicable
Reserved
0
0
Not Applicable
Reserved
Byte 6: Vendor/Revision ID Register
Bit
@Pup
Pin#
Name
Pin Description
7
0
–
–
Revision ID Bit 3
6
0
–
–
Revision ID Bit 2
5
0
–
–
Revision ID Bit 1
4
0
–
–
Revision ID Bit 0
3
1
–
–
Vendor ID Bit 3
2
0
–
–
Vendor ID Bit 2
1
0
–
–
Vendor ID Bit 1
0
0
–
–
Vendor ID Bit 0