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3.5.5 Power Switch Interface
The power switch interface of the PCI7x21/PCI7x11 controller is a 3-pin serial interface. This 3-pin interface is
implemented such that the PCI7x21/PCI7x11 controller can connect to both the TPS2226 and TPS2228 power
switches. Bit 10 (12V_SW_SEL) in the general control register (PCI offset 86h, see Section 4.31) selects the power
switch that is implemented. The PCI7x21/PCI7x11 controller defaults to use the control logic for the TPS2228 power
switch. See Table 3−3 and Table 3−6 below for the power switch control logic.
Table 3−3. TPS2228 Control Logic—xVPP/VCORE
AVPP/VCORE CONTROL SIGNALS
OUTPUT
V_AVPP/VCORE
BVPP/VCORE CONTROL SIGNALS
OUTPUT
V_BVPP/VCORE
D8(SHDN) D0 D1 D9
OUTPUT
V_AVPP/VCORE
D8(SHDN) D4 D5 D10
OUTPUT
V_BVPP/VCORE
1 0 0 X 0 V 1 0 0 X 0 V
1 0 1 0 3.3 V 1 0 1 0 3.3 V
1 0 1 1 5 V 1 0 1 1 5 V
1 1 0 X Hi-Z 1 1 0 X Hi-Z
1 1 1 0 Hi-Z 1 1 1 0 Hi-Z
1 1 1 1 1.8 V 1 1 1 1 1.8 V
0 X X X Hi-Z 0 X X X Hi-Z
Table 3−4. TPS2228 Control Logic—xVCC
AVCC CONTROL SIGNALS
OUTPUT
V_AVCC
BVCC CONTROL SIGNALS
OUTPUT
V_BVCC
D8(SHDN) D3 D2
OUTPUT
V_AVCC
D8(SHDN) D6 D7
OUTPUT
V_BVCC
1 0 0 0 V 1 0 0 0 V
1 0 1 3.3 V 1 0 1 3.3 V
1 1 0 5 V 1 1 0 5 V
1 1 1 0 V 1 1 1 0 V
0 X X Hi-Z 0 X X Hi-Z
Table 3−5. TPS2226 Control Logic—xVPP
AVPP CONTROL SIGNALS
OUTPUT
V_AVPP
BVPP CONTROL SIGNALS
OUTPUT
V_BVPP
D8(SHDN) D0 D1 D9
OUTPUT
V_AVPP
D8(SHDN) D4 D5 D10
OUTPUT
V_BVPP
1 0 0 X 0 V 1 0 0 X 0 V
1 0 1 0 3.3 V 1 0 1 0 3.3 V
1 0 1 1 5 V 1 0 1 1 5 V
1 1 0 X 12 V 1 1 0 X 12 V
1 1 1 X Hi-Z 1 1 1 X Hi-Z
0 X X X Hi-Z 0 X X X Hi-Z
Table 3−6. TPS2226 Control Logic—xVCC
AVCC CONTROL SIGNALS
OUTPUT
V_AVCC
BVCC CONTROL SIGNALS
OUTPUT
V_BVCC
D8(SHDN) D3 D2
OUTPUT
V_AVCC
D8(SHDN) D6 D7
OUTPUT
V_BVCC
1 0 0 0 V 1 0 0 0 V
1 0 1 3.3 V 1 0 1 3.3 V
1 1 0 5 V 1 1 0 5 V
1 1 1 0 V 1 1 1 0 V
0 X X Hi-Z 0 X X Hi-Z
3.5.6 Internal Ring Oscillator
The internal ring oscillator provides an internal clock source for the PCI7x21/PCI7x11 controller so that neither the
PCI clock nor an external clock is required in order for the PCI7x21/PCI7x11 controller to power down a socket or
interrogate a PC Card. This internal oscillator, operating nominally at 16 kHz, is always enabled.