
Principles of Operation
48
September 2005
SCPS110
3.5.1 PC Card Insertion/Removal and Recognition
The PC Card Standard (release 8.1) addresses the card-detection and recognition process through an
interrogation procedure that the socket must initiate on card insertion into a cold, nonpowered socket. Through
this interrogation, card voltage requirements and interface (CardBus versus 16-bit) are determined.
The scheme uses the card-detect and voltage-sense signals. The configuration of these four terminals
identifies the card type and voltage requirements of the PC Card interface.
3.5.2 Low Voltage CardBus Card Detection
The card detection logic of the PCIxx12 controller includes the detection of Cardbus cards with VCC = 3.3 V
and VPP = 1.8 V. The reporting of the 1.8-V CardBus card (VCC = 3.3 V, VPP = 1.8 V) is reported through the
socket present state register as follows based on bit 10 (12V_SW_SEL) in the general control register (PCI
offset 86h, see Section 4.30):
If the 12V_SW_SEL bit is 0b (TPS2228 is used), then the 1.8-V CardBus card causes the 3VCARD bit
in the socket present state register to be set.
If the 12V_SW_SEL bit is 1b (TPS2226 is used), then the 1.8-V CardBus card causes the XVCARD bit
in the socket present state register to be set.
3.5.3 PC Card Detection
The PC Card Standard addresses the card detection and recognition process through an interrogation
procedure that the socket must initiate upon card insertion into a cold, unpowered socket. Through this
interrogation, card voltage requirements and interface type (16-bit vs. CardBus) are determined. The scheme
uses the CD1, CD2, VS1, and VS2 signals (CCD1, CCD2, CVS1, CVS2 for CardBus). A PC Card designer
connects these four terminals in a certain configuration to indicate the type of card and its supply voltage
requirements. The encoding scheme for this, defined in the PC Card Standard, is shown in Table 32. In
addition, to 16-bit and CardBus cards, the controller supports the detection of USB custom cards via the
custom card detection method defined by the PC Card Standard. Other types of custom cards are not
supported and if detected the socket registers will report values as if it were empty.