C9577
Low EMI Clock Generator/Buffers for Pentium® II Systems
Preliminary
POWER MANAGEMENT FUNCTIONS
Power management function is controlled at pins 29, 30, and 31 inputs PD# (PWR_DWN#), CS# (CPU_STOP#), and PS#
(PCI_STOP#) respectively. These inputs have internal pull ups, and are active LOW. Therefore, if these pins are floating, they will
default to a high state and do not effect the device. Typically these inputs are controlled by the South Bridge chipset.
The clocks may be disabled according to the following tables 3 and 4 in order to reduce power consumption. All clocks are
stopped in the low state, see fig.2. All clocks maintain a valid high period on transitions from running to stopped. The CPU and PCI
clocks transition between running and stopped by waiting for one positive edge on PCI_F followed by a negative edge of their own
clock. PCI_F is the clock that times the power management function in the South Bridge, therefore it does not stop until PD# = 0.
CS#
PS#
PD#
CPU(1:4)
PCI(1:7)
OTHER CLKs
XTAL & VCOs
x
0
0
0
0
1
1
1
1
x
0
0
1
1
0
0
1
1
0
1
1
1
1
1
1
1
1
LOW
LOW
LOW
LOW
LOW
OFF
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
RUNNING
LOW
LOW
LOW
RUNNING
RUNNING
LOW
LOW
RUNNING
RUNNING
RUNNING
RUNNING
LOW
RUNNING
RUNNING
Table 3
NOTE1: all clocks can be individually enabled / stopped via the I2C interface. In this case all clocks are stopped asynchronously in the low state.
Power Management Timing Table
Signal
Signal State
1 (disabled)
Latency
CS#
1 rising edge of CPU_F
1 rising edge of CPU_F
1 rising edge of PCI_F
1 rising edge of PCI_F
2 mS
0 (enabled)
1 (disabled)
0 (enabled)
1 (disabled)
0 (enabled)
PS#
PD#
1 rising edge of PCI_F
Table 4
POWER MANAGEMENT TIMING
PC I_F
PS#
wait c y c le
s tops on nex t f alling edge
PC I(1:7)
C S#
wait c y c le
s tops on nex t f alling edge
C PU (1:4)
Fig. 2
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 TEL: 408-263-6300 FAX 408-263-6571
Rev 1.5
4/22/1999
Page 3 of 10
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