Z9972
Document #: 38-07088 Rev. *D
Page 5 of 9
Power Management
The individual output enable/freeze control of the Z9972
allows the user to implement unique power management
schemes into the design. The outputs are stopped in the logic
“0” state when the freeze control bits are activated. The serial
input register contains one programmable freeze enable bit for
12 of the 14 output clocks. The QC0 and FB_OUT outputs can
not be frozen with the serial port, this avoids any potential lock
up situation should an error occur in the loading of the serial
data. An output is frozen when a logic “0” is programmed and
enabled when a logic “1” is written. The enabling and freezing
of individual outputs is done in such a manner as to eliminate
the possibility of partial “runt” clocks.
The serial input register is programmed through the SDATA
input by writing a logic “0” start bit followed by 12 NRZ freeze
enable bits. The period of each SDATA bit equals the period of
the free running SCLK signal. The SDATA is sampled on the
rising edge of SCLK.
D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 D11
D0-D3 are the control bits for QA0-QA3, respectively
D4-D7 are the control bits for QB0-QB3, respectively
D8-D10 are the control bits for QC1-QC3, respectively
D11 is the control bit for SYNC
Start
Bit
Figure 2. SDATA Input Register
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