ExpressCard™ Standard Summary
This document provides an overview of the Personal Computer Memory Card International Association’s (PCMCIA) ExpressCard Standard. It summarizes the ExpressCard electrical, module, connector, and host system specifications that can be found in the ExpressCard Standard.
This document is being provided by the PCMCIA to assist product developers in understanding the features and capabilities of ExpressCard technology. It is not intended to be used as a technical specification in the design or development of any product.
The ExpressCard Standard is available at no charge to PCMCIA members. Non-members may purchase the ExpressCard Standard at http://www.pcmcia.org/order.htm.
For information about the PCMCIA see http://www.pcmcia.org/about.htm. For PCMCIA membership information see http://www.pcmcia.org/application.htm.
Introduction
An ExpressCard module is a small, modular add-in card technology intended to be used in desktop and mobile computing platforms. Figure 1 illustrates two examples of ExpressCard applications.
 
Figure 1: ExpressCard concepts in desktop and mobile computing platforms
The ExpressCard solution accommodates the replacement of conventional parallel buses for I/O devices with scaleable, high-speed serial interfaces. Two classes of serial interfaces are implemented by this solution, PCI Express, a high performance, integrated I/O interconnect solution, and USB for the ease of upgrading PC Card technologies and integrating popular external peripheral functionality via the ExpressCard module form-factor.
Two standard module formats are specified: an ExpressCard/34 module and an ExpressCard/54 module. The ExpressCard solution is designed to support a universal slot configuration that allows either ExpressCard/34 or ExpressCard/54 modules to function in the same slot. Host solutions that implement slots that only support ExpressCard/34 modules are also allowed by this standard.
The ExpressCard architecture is based on an extensible, modular implementation, allowing multiple slots (see Figure 2). In any multi-slot host implementation, all slots provide equivalent I/O interface functionality. Both module formats afford access to the same I/O interface performance and source power although the larger ExpressCard/54 module affords the application nominally 140% the internal volume and 160% the thermal dissipation capacity over the ExpressCard/34 module.
Figure 2: Modular implementation concept
PCI Express is a dual-simplex 2.5 Gbps differential serial link solution standardized by the PCI Special Interest Group (PCI-SIG). USB 2.0 is a full-duplex 480 Mbps differential serial bus solution standardized by the USB Implementers Forum (USB-IF). The ExpressCard Standard defines the modular implementation of the PCI Express and USB 2.0 based on normative references to each interface’s baseline specifications as defined within their respective parent organizations.
Each slot of the ExpressCard host interface must support a single PCI Express lane. The ExpressCard host interface must also support the low-, full- and high-speed USB data rates. Support of both interfaces is a condition for being a ExpressCard-compliant host platform.
ExpressCard Interface
The ExpressCard interface consists of two primary I/O busses, PCI Express and USB, and power supplied by the host system delivered through a 26 pin connector. A host system is required to support both PCIe and USB busses. An ExpressCard module may implement either one or both of the standard interfaces depending on what the requirements are for the application. See table 1 for a list of ExpressCard interface signals.
Table 1: ExpressCard Interface — List of signals
|
Signal Group |
Signal |
Description |
Interface Type(s) on module |
Host |
|
PCI Express |
USB |
Both |
|
PCI Express |
PETp0, PETn0, PERp0, PERn0 |
PCI Express x1 interface |
R |
NC |
R |
R |
|
REFCLK+, REFCLK- |
PCI Express reference clock |
R |
NC |
R |
R |
|
PERST# |
PCIe Reset |
R |
NC |
R |
R |
|
USB |
USBD+, USBD- |
USB serial data interface |
NC |
R |
R |
R |
|
SMBus |
SMBDATA, SMBCLK |
SMBus |
Opt |
Opt |
Opt |
Opt |
|
System
Auxilliary
Signals |
CPPE# |
PCI Express interface presence detect |
R |
NC |
R |
R |
|
CLKREQ# |
Request that REFCLK be enabled |
R |
NC |
R |
Opt |
|
WAKE# |
Request that the host interface return to full operation and respond to PCI Express |
Opt |
NC |
Opt |
Opt |
|
CPUSB# |
USB interface presence detect |
NC |
R |
R |
R |
|
Power |
+3.3 V
(2 Pin) |
Primary voltage source, 3.3V |
R |
R |
R |
R |
|
+3.3 VAUX
(1 Pin) |
Auxiliary voltage source, 3.3VAUX |
Opt |
Opt |
Opt |
R |
|
+1.5 V
(2 Pins) |
Secondary voltage source, 1.5V |
Opt |
Opt |
Opt |
R |
|
GND
(4 Pins) |
Return current path, Ground |
R |
R |
R |
R |
Module Detection and Operation
Module detection and operation consists of the following fundamental elements.
- State of CPPE# and CPUSB#
- State of PERST# (for PCI Express-based modules only)
- REFCLK to the slot based on the state of CPPE# and/or CLKREQ#
- Wakeup requests based on the state of WAKE# (PCI Express-only)
- I/O interface detection, set-up and operation based on the in-band capabilities of the appropriate interface, either PCI Express, USB, or both
PCI Express power control operation
On power up, the de-assertion of PERST# is delayed from the power rails achieving operating limits to allow adequate time for the power to stabilize on the module and certain system functions to start prior to the module starting up.
If the host system enters a power saving state that will cause the primary power sources to turn off, e.g. S3 or S4, a module must be placed into a D3 state prior to any power transitions at the slot.
During the D3 state, both +3.3V and +1.5V may be turned off while +3.3VAUX remains powered.
As soon as the supplies are out of their specified tolerance range, PERST# is asserted. Modules should not assume that PERST# will provide advanced warning of a loss of power. +3.3VAUX may remain valid for host system sleep and off states even if the device is not enabled for wakeup events.
USB power control operation
USB modules are responsible for deriving any necessary functional reset based on the state of the power being supplied to the module. USB modules are also responsible for combining as needed primary and auxiliary power to meet the needs of the application while maintaining required isolation between the separately supplied power rails.
I/O interface detection, set-up and operation
For all ExpressCard modules, the module must be detected before the socket can be powered and the supported interfaces can be enabled.
PCI Express module insertion model
Once power is applied, the PCI Express interface must be enabled on both the module and the host in order that the native detection and configuration protocols of the data interface can begin.
USB module insertion model
Once power is applied, the USB module operation closely follows the USB connection model that exists with USB walk-up connectors and external USB devices.
ExpressCard Module
This section summarizes the module’s physical outline dimensions, electrical, mechanical, and environmental requirements. Each module manufacturer is responsible for qualification of their products to this specification.
Module Dimensions
There are two formats of the standard ExpressCard modules in this specification: the ExpressCard/34 module characterized by its 34 mm width and the ExpressCard/54 module characterized by its 54 mm width. Figure 3 and Figure 4 define the outline dimensions for the ExpressCard/34 module and ExpressCard/54 module, respectively.
 |
 |
Figure 3: ExpressCard/34 module
outline dimensions |
Figure 4: ExpressCard/54 module
outline dimensions |
The following features are worth noticing:
- ExpressCard/34 modules and ExpressCard/54 modules use the same connector interface.
- The EMI ground clips on the module are optional. If implemented, they must be located in the positions specified.
- An alternative shape is allowed on the back side of the module in the connector placement area.
This specification also defines extended module formats to allow applications to use existing standard I/O connectors, incorporate external antennas, or implement other extended applications.
Extended length is for reference only. Module manufacturers have the flexibility to increase or reduce it to suit their application needs. Similarly, extended module height is also for reference only. Module manufacturers can decide their own extended module heights.
Module Thermal Requirements
Electrical power consumption limits for ExpressCard modules are defined. Modules shall be designed to operate in a confined, still air environment in a temperature consistent with a typical host system environment. As a result, module manufacturers and system manufacturer should design to the Thermal Design Power (TDP) requirements.
Environmental and Mechanical Requirements
The ExpressCard module environmental testing consists of:
- Operating & Storage Environment
- High & Low Storage & Operating Temperature
- Thermal Shock
|
- Moisture Resistance
- Vibration and High Frequency
- Shock & Drop Test
|
Labeling (Marking)
The thickness of labeling, if used, shall not cause the ExpressCard module to exceed the thickness specified in the module outline figures.
The label, if used, must withstand all environmental tests as specified
Host System Slot
This chapter summarizes the host system requirements. Host system ExpressCard electrical and mechanical design guides and design examples are covered in the ExpressCard Implementation Guidelines
Slot power control requirements
Power to ExpressCard slots is controlled by implementation-specific hardware within the host system. The module presence pins are asserted by the presence of ExpressCard modules inserted into the slot and are intended to enable the power rails to the module so that the module can perform its intended operation.
There are three common system conditions (ON, OFF, and SLEEP) during which the module presence logic should be used by the system to determine whether or not to provide power to the slot. If a module is inserted into the system during the OFF or SLEEP states, power is not applied upon module insertion. When a module is inserted during system ON state then power is applied to the module. If a module is already inserted into the slot when the host system powers up or resumes from a SLEEP state then power is applied to the module.
PCI Express Slot Capabilities Register
The PCI Express Base Specification defines a slot capabilities register that in an ExpressCard system implementation shall be required for each upstream port associated with an ExpressCard slot. Because of the ExpressCard operational model is hot pluggable and allows surprise insertion/removal of modules, both the Hot-Plug Surprise and Hot-Plug Capable bits shall be hardware initialized to the set state for each ExpressCard slot.
BIOS ACPI Requirements
In order to support ExpressCard module implementations that feature utilization of both the PCI Express and USB interface being used at the same time, the operating system must be able to determine the dependencies between the two buses. This information is used when an eject request is received. Without understanding the inter-dependencies of the two interfaces, executing a request to turn off one device may cause undesirable effects on the other device.
The mechanism used to define the dependency is an ACPI entry and is defined by BIOS as the result of decisions made when the host platform is designed. The ACPI entry is _EJD, and is used to convey eject dependencies.
Any host platform implementing ExpressCard sockets with ports provided by motherboard resident host controllers must complete the _EJD ACPI BIOS table entry.
ExpressCard Connectors
A beam-on-blade style connector is used for the ExpressCard interface. Although there are two module form factors (ExpressCard/34 module and ExpressCard/54 module), there is only one common connector interface for both module formats. This chapter summarizes the connector requirements.
Module Connector
The blade contacts are located on the ExpressCard module.
Only the front-end of the module connector that interfaces with the host connector is defined. The back-end of the connector that interfaces with the module printed circuit board is not defined.
 
Figure 5: Module connector views
It is recommended that the module connectors be surface-mounted. The pads on the footprint shall be numbered.
Note that the recommended module connector footprint does not include any mechanical hold-down feature to protect the solder joints of the connector from being damaged during the repetitive module insertion/extraction. Module and connector manufacturers are responsible for ensuring the mechanical integrity of the ExpressCard module connector.
Host Connector
The ExpressCard host connector is summarized in Figure 6. This connector accommodates either the ExpressCard/34 modules or ExpressCard/54 modules.
 
Figure 6: Host connector views
Mechanical hold-down features are required for the host connector to survive the mating/un-mating forces encountered during module insertion and removal. Although SMT pads are illustrated, other features such as screws or through-hole solder joints are also allowed at each system manufacturer’s discretion.
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Collateral Material
