General knowledge about the use of PCMCIA cards
PCMCIA (abbreviation of Personal Computer Memory Card International Association PC Memory Card International Federation) is an international organization established in 1989. It is an international standards organization and trade federation with more than 300 member companies. Its members include internationally renowned companies such as Intel, AMD, IBM, Compaq and TI. This international organization is mainly to establish a power-saving, small-volume integrated electronic card standards, improve the interchangeability of mobile computers.
PCMCIA introduced the first product applicable to this standard-the memory card. At the same time, the specification of 68 pin was also determined. Also added slot instructions. Manufacturers realize that software needs to improve compatibility, so this standard has been applied accordingly. But there are more and more applications that require large and fast data access-such as multimedia and high-speed networks. In order to meet this demand, PCMCIA has formulated two other new specifications-CardBus and Zoomed Video, which enable 100 Mbit Ethernet and Mpeg compression formats to be implemented on PCMCIA. Because of the increasing speed, PCMCIA has been supplementing this specification to improve compatibility and take into account other aspects of mobile motivation. In addition to the speed increase, PCMCIA has also developed a 3.3V standard to make PCMCIA cards more power efficient.
In the early days, the PCMCIA cards we used were all 16BIT, and the PCcard of 16BIT was slow. As far as the network card is concerned, even if it is a 100M network card, the actual use speed is only about 25M m. Now the general use of PCMCIA cards are 32bit CardBus cards, operating frequency of 33MHz, speed has been able to meet the general LAN and broadband applications. If you are more careful, you will find that the PCMCIA slots on the notebook now are divided into TYPEI, TYPEII and TYPEIII. These three PCMCIA interfaces have been developed from I to III and are compatible downward. TYPEI/II is the common single PCMCIA slot design we usually use, while the double slot is TYPEIII. (Due to the rapid development of notebook computers, the demand for light, thin, short and small expansion devices has increased greatly. In order to meet the needs of each product design, PCMCIA has developed three thickness specifications for electronic cards-Type I, Type II and Type III. The order gets thicker and thicker from small to large. Type I-3.3MM,Type II-5.0MM,Type III-10.5MM. Except for the thickness, the length and width of the cards of the three specifications are exactly the same.)
  
PCMCIA card
Weight: about 1 ounce about 0.5 ounces
Volume: 85.6x 54.0mm 42.8 x36.4mm
　　规　 格：TypeI(3.3mm)、TypeII(5.0mm)、TypeIII(10.5mm)、Card Bus、Zoom Video TypeI(3.3mm)、TypeII(5.0mm) 
Application range: widely used in notebook computers. Generally speaking, it consumes more electricity, but the cost is lower.
PCMCIA slot is the most important device expansion interface on notebook computers, which can be used to insert fax cards/network cards/memory cards/sound blaster cards, etc. Some professional magazines even predict that PCMCIA will become the standard interface on desktop computers, automobiles and household appliances in the future. The main advantage of PCMCIA is that it can be plugged and unplugged with power, and plug and play can be realized with appropriate software.
Although everyone is optimistic about the development prospect of PCMCIA, the current users have to face many problems. At present, PCMCIA cards, PCMCIA slots and slot driver software on the market do not follow strict and consistent standards. There are problems in the compatibility of products from various manufacturers. It is better for ordinary users to find professional notebook computer vendors to provide installation and debugging services when purchasing. Each notebook computer will be provided with the original PCMCIA slot driver software at the time of sale. Users should pay attention to backup and preservation. This software is necessary when adding PCMCIA expansion cards.
If the latest notebook computer has a "ZV" mark on its PCMCIA slot, it means it can support the latest movie decompression card, video display system-related expansion equipment such as video display card. If the PCMCIA slot has a "CB" mark, it means it can support the latest 32-bit CARD BUS bus, and the PCMCIA interface has a higher data transmission rate.
At present, in addition to notebook computers can use PCMCIA specification cards, there are PDA, digital camera, digital TV, set-top boxes (set-top boxes)... And so on also have corresponding products can use PCMCIA specifications of the card.
In order to meet the demand for high speed in multimedia and network applications, PCMCIA promulgated the 68-pin PC card standard for memory cards in 1991, and newly formulated CardBus and ZV interface standards in 1995 to enable notebooks to connect PCI devices, such as high-speed network cards, video capture/video conference cards, SCSI cards, etc. The following two articles will explain the contents of the CardBus and ZV standards respectively.
Introduction to CardBus Interface
CardBus is PCMCIA's next-generation high-performance 32-bit bus master interface. It enables advanced features that are now available only on desktops and larger systems to be moved to the CardBus card for use in a mobile environment. New features developed for CardBus can also be used on 32-bit desktop systems if they are equipped with CardBus slots.
Properties of the CardBus Interface
CardBus adds important functionality to the PC Card and is compatible with the new features of the new PC Card standard. Features and functions of the CardBus interface include 32-bit address and data, 33MHz operating frequency and bus master operation.
· CardBus interface support up to 33MHz operating speed, for the expansion of PC card users existing applications to create the conditions.
· The CardBus interface supports multiple bus functions in any combination. The bus master function can share tasks with processors, which can help improve system throughput in a multi-job environment.
• CardBus support PC Card's existing Audio Digital Waveform (ADW) mode and new Pulse Width Modulation (PWM) mode. Either of these two modes can be used in the CardBus, but must be approved by the system software before use. The operating range of PWM audio is much better than that of ADW audio. Although the CardBus is defined with platform independence in mind, the interface is designed for 32-bit systems. Systems with 16-bit buses benefit little from this interface. CardBus specifications greatly enhance the interchangeability between systems.
CardBus working principle
The signal transmission protocol of the CardBus interface originates from the PCI area bus signal transmission protocol. There are some differences between the two, but most functions have the same operation.
CardBus software models can be shared with 16-bit PC cards. Since its 32-bit Card Services (Card Service) interface is also defined for 16-bit PC cards, this interface can be used to manage both CardBus cards and non-CardBus cards.
Since CardBus cards and slots use the low voltage key defined for 3.3 volt cards, CardBus cards must be designed to use 3.3 volts or less, which results in lower system power consumption and longer battery life.
In the initial power-on or reset operation, the power consumption of the CardBus card must be limited to ensure that the information can be read from the CardBus card, and thus determine whether the system can provide sufficient power and other hardware resources to ensure the normal operation of the CardBus card. The limitation of the power supply prevents excessive transient current consumption of the battery and smoothly rejects the CardBus card when the power required for operation cannot be provided.
The CardBus slot shall accept and support all 16-bit PC cards in accordance with the conditions set forth by the host system. The CardBus interface supports hot-plugging of the card. When the card is not inserted, the slot must be powered off, and when the card is inserted, the slot is powered on. For users, it's like hot-plugging.
Adapter
As mentioned earlier, the CardBus must also support non-CardBus PC cards. When a card is inserted into the slot, the PC asks to determine if it needs CardBus support, and then adds the appropriate power and other resources as appropriate. This prevents damage to the inserted board.
The card detection/voltage detection (Card Detect/Voltage Sense) algorithm is designed. All CardBus and low-voltage non-CardBus cards support this algorithm. It enables the CardBus adapter to recognize any PC card in any slot. The information provided by the adapter enables the appropriate software to determine whether the inserted card can be supported and, if not, to reject it smoothly.
System Software
Socket Services software is provided regardless of whether an adapter supports CardBus. However, different adapter designs require different Socket Services implementations. Single-host systems may include adapters that support and do not support CardBus. Therefore, the corresponding Socket Services handler can also be hosted on the same single-host system. All adapters require very little Socket Services functionality.
Card Services software is used to provide brief information about the specific functions and status of all PC cards. When only CardBus support is required, only minor modifications are CardBus required. However, when full compatibility is required for CardBus and non-CardBus, significant changes are required within the Card Services.
Configuration
When the insertion of a PC card is detected, the PC will establish the voltage and signal transmission protocols required by the PC card. If the system supports the voltage and other requirements of the card, the PC will provide the appropriate signal transmission protocol and voltage; otherwise, the user will be informed that the card cannot work in this system. Once a card is recognized, the card can only get a limited current in case of excessive battery current. The configuration operation may also be implemented by a general-purpose circuit. The CardBus interface also provides support for multifunction CardBus cards.