VG-469, PCMCIA White Paper
White Paper: A Superior PC Card Socket Controller for Desktop Systems
Document No. WP-000038-01
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Introduction
Personal computers have revolutionized the way people work. Today, PCs are used in a wide range of settings and have become a primary business tool. With these innovations, however, have come new industry challenges. Configuring PC hardware and operating systems to work with different peripheral devices can be a significant problem. Changing the hardware configuration of a machine is a task few end-users attempt, and even trained technicians can find configuration to be difficult, time-consuming, and frustrating.
A broad base of companies within the computer industry, however, is addressing these problems with a technology known as plug-and-play (PnP), which gives consumers the ability to add or remove hardware in PC systems without worrying about switch settings or hardware conflicts. This technology was originally designed for the PC Card industry but has since effectively migrated to the desktop platform. Most of the PC add-on cards now come with the PnP feature, and naturally, the ISA host adapters for the PC Card socket controller have to support this technology as well.
This paper reviews some key issues of integrating the PC Card socket controller into the desktop computer. It also discusses solutions Amphus provides for PC Card support in a desktop system.
Executive Summary
As a larger number of PC Card-based products have become vailable, more desktop systems are now equipped with PC Card slots. As a result, demand for PC Card Socket Controllers is also growing.
Amphus has designed a full line of PC Card Socket controllers to fill the increasing need for interfacing PC Cards to the host. Amphus’s product line ranges from the fully featured VG-469 controller to those for use in space-limited and cost-sensitive applications.
Amphus’s VG-469 PC Socket controller has the following features:
- 82365SL compatibility
- Mixed voltage support (for both 5 V and 3.3 V card and host systems)
- PC Card DMA
- ISA bus Plug-and-Play
- Driver for activity LED indicator
- Low-voltage card protection
- Control signals for buffered cable
The VG-469 is a plug-and-play solution, which eliminates the need to configure jumpers or change switch settings to the host adapters. Other features, such as hot insertion and very low power consumption make Amphus’s PC Card Socket controllers an excellent choice for today’s platforms with PC Card access.
PC Card and Desktop PC
PC Card (formerly PCMCIA) was designed to provide resources that users could add to and remove from a system without rebooting or turning off the host. PC Card technology not only offers the users a simple way to add more memory or additional peripherals to a machine, but also provides a convenient means for resource sharing among systems. Another benefit of the technology is that it gives users a quick way of safeguarding data, which improves system security.
The market for PC Cards has been expanding rapidly, and the PC Card industry forecast continues to be healthy. According to Andrew Prophet Research and Consulting, over 4.5 million PCs shipped in 1995 contained at least one PC Card slot. In 1999, just three years from now, the total number of platforms shipped will be in exceed of 29 million. On the card side, by the end of this year, over 20 million PC cards will be shipped, and in 1997 that number will be well over 33 million. Furthermore, the Department of Defense’s recent decision to make PC Card slot a necessity for all their PC procurements will further promote the growth of this market.
Although the driving force behind the PC Card has been the portable industry, the trend is changing. More desktop systems now are equipped with PC Card slots. The reason is that there is a large number of PC Card-based products now available. Some of the peripheral devices currently available are: Hard Drives, CD-ROM Interface, Docking Station, Data Acquisition Devices, Memory Cards and Video Capture Cards. And the fact that desktop users don’t need to open up their systems to install and configure a new piece of hardware is very appealing.
The hardware that establishes the interface between the PCMCIA bus and the host bus is called "PC Card Socket Controller" and is usually implemented in a stand-alone IC or with other functions in a system. Different silicon vendors provide different solutions for this component.
Amphus’s PC Card Socket Controller Solution
Amphus’s VG-469 is a fully-featured, Intel 82365SL-compatible, socket controller. The VG-469 directly supports two sockets with hot-insertion. For systems requiring more than two sockets, VG-469s can be cascaded to support up to four sockets with no glue logic. For larger systems, any number of these controllers can be cascaded with minimal external logic. Besides supporting mixed voltage cards, the controller can operate in both 5V and 3.3V host systems. Other features include PC Card DMA, ISA bus Plug-and-Play, a driver for an activity LED indicator, low-voltage card protection, and control signals for different buffered cable schemes. The VG-469 controller is perfectly suited for desktop systems.
Plug-and-Play (PnP) Support:
Most desktop PCs don’t come with a built-in PC Card interface on the mother board. To add this capability to the system, end-users usually go with the add-on board solution. The notorious inconveniences during system configuration (such as I/O port allocation, interrupt request assignment, DMA channels, and address ranges) are sometimes troublesome. The reason for this problem is that the added hardware usually has jumpers or switches for setting up the parameters mentioned. Once configured, the jumpers not easily changed on-the-fly.
In a typical situation, an incorrect jumper setting makes the add-on card non-functional. In a more severe case, the set-up conflicts among different hardware may hang the system. Unlike most of the ISA socket controllers on the market that possess the annoying problem of resource allocation conflict, the VG-469 has solved this problem with its integrated plug-and-play capability.
To alleviate the irritating resource conflict issue, the Plug-and-Play ISA Specification provides a mechanism to automatically configure any ISA card on the bus. In general, the PnP system executes the following steps in the process of auto-configuration:
- Isolate the card.
- Read the card’s resource data.
- Identify the card and configure its resource.
- Locate a driver for the card.
From the hardware standpoint, the plug-and-play specification defines a set of configuration registers located at pre-defined I/O addresses that all PnP devices must implement. The PnP software accesses these registers in the resource allocation process. When a card is identified, either by the BIOS (in a PnP compatible BIOS system) or by the operating system (in a non-PnP BIOS system), the card sends the device ID to the operating system. The operating system then uses the device ID to access the correct driver for the card.
The plug-and-play function integrated into Windows 95 supports a wide variety of devices. Amphus’s VG-469 PC Card socket controller is one of the supported devices. Configuration information stored in a serial EEPROM allows the host to find the appropriate software driver for the VG-469.
This information is then used to find the PnP driver for the VG-469. Once the driver has loaded, the VG-469 system is configured and the socket is ready to communicate with the PC Card. The configuration process described above is fully automatic. There is no user-required input. This simplicity cannot be achieved on a system without a plug-and-play PC Card socket controller. In a non-PnP socket controller system, there are usually multiple jumpers or switches that must be verified or changed. On a highly populated desktop PC, this manual configuration is even more of a problem.
In conclusion, the plug-and-play feature allows flexibility of resource allocation in any type of system. With plug-and-play ISA support, desktop PCs with either one or multiple controllers can automatically relocate the socket controllers to any available address. PnP also benefits notebook systems with docking stations.
PC Card and PCI bus
Currently, PC Card software drivers do not support PCI’s interrupt structure. Existing PC Card socket controllers interfacing with the PCI bus generally carry sideband ISA interrupt signals that must plug into an ISA slot. This solution is clearly not desirable. To remain compatible with the vast number of existing PC Card socket controllers on the ISA bus, client drivers are not likely to change. As a result, a PC Card socket controller on the ISA bus is still the best solution.
Compatibility
The PCMCIA group has produced a well-defined specification for the PC Card adapter, but has not defined a standard architecture for the socket controller. Because of that, various design approaches have been employed by various silicon vendors, which may cause support problems for software developers.
Intel Corporation introduced the first socket controller (82365SL), which was designed for the ISA bus. The 82365SL has been very well-supported by software driver vendors. Recognizing the wide support of the 82365SL, Amphus has made the VG-469 upward-compatible with the 82365SL register set, which helps minimize software driver development time, reducing product time to market.
The Exchangeable Card Architecture Specification (ExCA) has further helped the socket controller industry to somewhat standardize controller architecture. For instance, the ExCA specification requires that the PC Card’s memory and I/O address space map directly into the CPU’s memory and I/O space, respectively. Register-based socket controllers cannot comply with this requirement. Also, according to ExCA, a minimum of five memory windows addressable in 4K blocks on 4K boundaries or a minimum of two I/O windows located on 1-, 8-, 16-, or 32-byte boundaries must be allowed. Furthermore, the ExCA specification recommends that the interrupt from the PC Card be steered to any one of the 10 IRQs on the ISA bus.
Note that not all socket controllers available on the market meet all these requirements. Again, the VG-469 and all other socket controllers designed by Amphus are fully compliant with this specification, preserving your investment.
Card Protection
The PC Card standard (version 2.1) requires mixed-voltage operation–the socket must provide 5 volts, 3.3 volts, or even lower voltages to the card. This versatility obviously requires some mechanism to prevent a 3.3-volt card from being damaged by a 5-volt supply. To avoid this problem, the PC Card specification recommends the use of a keyed connector for the socket. However, a keyed connector alone cannot always guarantee protection of a low-voltage card, since an incorrect driver or even a software glitch may inadvertently command the socket controller to send 5-volt power to a 3.3-volt card.
The VG-469 has a voltage-limit feature that protects a 3.3-volt card from being powered by a 5-volt supply from the socket. This feature is very important for a desktop system because most desktop PCs operate at 5 volts, while many PC cards are designed for a lower voltage environment.
Cable Buffering
Most of the PC Card hard drives for desktop PCs consist of two physical cards–one plugged into the ISA bus on the mother board, and the other mounted in the drive bay. These cards are generally connected together by ribbon cables. Different designs may have different schemes for the ribbon cable connection. For the design that places the socket controller IC on the ISA interface board, all the PC Card signals have to route to the appropriate socket. In a single-socket drive system, 68 signals need to be sent over the cable, usually requiring two 40-pin ribbon cables. In the dual-socket drive bay design, the number of signals is, of course, doubled. Because of signal quality concerns, these signals are usually buffered before transmitting to the ribbon cable.
The Amphus VG-469 chip provides control signals for different buffered cable methods. The control signals can be programmed for controlling the buffers located on the ISA bus or, alternatively, they can be programmed to control the buffers that are positioned on the drive bay. With this feature, the system designers save glue logic for controlling the signal buffers.
Other Features
If power consumption is a concern, the Amphus socket controllers are certainly the best choice. In addition to a low internal operating clock, all Amphus chips include an activity timer that can be programmed to further reduce the power consumption of the part. In power down mode, with all inputs static, the VG-469 controller consumes only 10 microamperes.
Another critical requirement for the PC Card interface is 'hot insertion' (the ability to insert and remove the card without powering-down the system). Hot insertion is usually implemented with several buffers and transceivers. The VG-469 contains these components on-board, which further reduces the design cost.
Besides their superior design, Amphus’s PC Card socket controllers are also supported by many major driver vendors. Amphus can also provide several proven reference designs to customers for fast time-to-market designs.
Competitor Offering
Very few 82365SL-compatible PC Card socket controller vendors have the plug-and-play feature built into their products. The DB86184 chip (made by Databook) has plug-and-play feature, but this chip is not 82365SL and ExCA compatible. And the power consumption of the DB86184 is about 40 MA in standby mode compared to 10 microamperes for the VG-469.
All Amphus’s socket controllers are compliant with PCMCIA 2.1/ExCA and JEIDA 4.1, and fully register-compatible with Intel 82365SL.
Summary
With continuing cooperation among the numerous members of the PCMCIA group, the future of the PC Card industry will certainly look better. As demand for PC Card grows, the system designer has little choice but to supply more platforms with PC Card access. To ensure smooth operation between the card vendors and the platform producers, designers must be very careful in selecting socket controllers. The most important factor in choosing the right controllers is, of course, adhering to industry standards. While this is true, the designers using PC Card socket controllers should also look beyond the basic characteristics of the PC Card standard, because features such as plug-and-play, protection for low-voltage cards, and advanced power management are no doubt very desirable to end users.
While many socket controller vendors have done a good job in meeting industry standards, only Amphus has managed to produce a PC Card socket controller that satisfies all the above requirements.
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