[Home]
[Edit this page]
[Recent Changes]
[Special Pages]
[Help]
PCMCIA BUS
PCMCIA BUS
This kind of Bus was formed in 1990. The full nomenclature of this bus is the Personal Computer Memory Card International Association (PCMCIA), this group developed a set of standards by which extra memory could be added to portable systems. It soon became obvious that this same interface could be used to add I/O devices and hard disk drives as well, thereby dramatically increasing functionality of laptop computers.
Today, just about any device available for desktop computers using an ISA or PCI bus is also available with a "PC-Card" interface for use with laptop computers, and in some cases, handheld machines.
The PCMCIA specification 2.0 release in 1991 added protocols for I/O devices and hard disks. The 2.1 release in 1993 refined these specifications, and is the standard around which PCMCIA cards are built today. PCMCIA cards are credit card size adapters, which fit into PCMCIA slots found in most handheld and laptop computers. In order to fit into these small size drives, PCMCIA cards must meet very strict physical requirements. There are three types of PCMCIA cards,
Implying, that individual cards access registers on the host system. Socket Services can be added to a computer as aDevice driver, or it can be built into PC BIOS
Immediately, on top of Socket Services in the hierarchy are the Card Services. Card Services is an application programming interface API which permits multiple software programs to work with multiple PCMCIA cards.
For instance, Card Services will allow both internet applications and fax applications to use an installed PCMCIA card modem. Like Socket Services, Card Services can be implemented as a device driver. It can also be built into a computer's operating system, as it is in Microsoft Windows 95/98/NT etc . Specifications PCMCIA specification 2.1 provides for a 16-bit bus interface, has a maximum clock speed of 10 MHz and is capable of speeds to 20 Mbps. The 2.1 spec. does not provide for bus mastering, DMA, or multiple interrupts. While PCMCIA provides only a minimal performance improvement over ISA, and does not come close in speed toPCI, it does provide for considerably more flexibility than either of the others. The two most important features of PCMCIA are its Plug and Play and Hot Swapping capabilities.
As with PCI, PCMCIA cards are truly Plug and Play--you simply insert them, and instructions coded into chips on the card provide the information a host needs to configure the cards and appropriately allocate resources. Not only are there no jumpers or switches to set, users never even see the inside of a PCMCIA card. It is simply inserted into the drive, and the system does the rest. In 1995, the PCMCIA 2.1 specification was enhanced to provide for 32-bit operation. The new architecture, called CardBus, was closely based on the PCI bus, and strove to provide the same improvements over the 16-bit PCMCIA card as PCI did over ISA. As such, CardBus provides for 33 MHz operation and correspondingly increased data transfer. It also introduces DMA and bus mastering to PCMCIA based systems, which can markedly increase performance. Realizing that there are still many 16-bit PCMCIA card peripherals in the marketplace CardBus is fully backward compatible with the older card design. Applications Though PCMCIA card use is not limited to portable computers, there are few instances where it is the best choice for data communication in desktop computers. In desktops, PCMCIA is better suited for adding extra storage space via hard-disk cards, or transferring large files from portable systems. However, for laptop and handheld computers, PCMCIA provides a way to connect a varied array of peripherals to the system, and to share those devices with a desktop computer. Clearly there is a size advantage to PCMCIA for portable applications. The cards are small, light, and have low power requirements. They are an ideal interface choice for peripherals that have been scaled down for portable use. Further, the ability to Hot Swap PCMCIA cards provides for the flexibility needed to use multiple peripherals with only one or two slots.USB and IEEE 1394 provide Hot Swapping are other alternatives for portable applications. IEEE 1394 uses a particularly small cable ideal for portable applications, and is ideal for high speed audio and video applications. However, to use USB or IEEE 1394, the peripheral devices in your system must be replaced with bus specific devices--an expensive prospect. Further, many USB products must be powered by the computer itself, thereby reducing the time a laptop can function on battery alone. Or, if too much power is required, they must be plugged-in, making them less attractive portable solutions. Nevertheless, if cost and power conservation are the primary concerns of the application, PCMCIA is still the best, most flexible choice for portable applications.
[Edit this page] [Page history] [What links here] [Discuss this topic] [Printer Friendly]
PCMCIA BUS
PCMCIA BUS
This kind of Bus was formed in 1990. The full nomenclature of this bus is the Personal Computer Memory Card International Association (PCMCIA), this group developed a set of standards by which extra memory could be added to portable systems. It soon became obvious that this same interface could be used to add I/O devices and hard disk drives as well, thereby dramatically increasing functionality of laptop computers.
Today, just about any device available for desktop computers using an ISA or PCI bus is also available with a "PC-Card" interface for use with laptop computers, and in some cases, handheld machines.
The PCMCIA specification 2.0 release in 1991 added protocols for I/O devices and hard disks. The 2.1 release in 1993 refined these specifications, and is the standard around which PCMCIA cards are built today. PCMCIA cards are credit card size adapters, which fit into PCMCIA slots found in most handheld and laptop computers. In order to fit into these small size drives, PCMCIA cards must meet very strict physical requirements. There are three types of PCMCIA cards,
- Type I generally used for memory cards such as FLASH and STATIC RAM
- Type II used for I/O peripherals such as serial adapters, parallel adapters, and fax-modems.
- Type III, which are used for rotating media such as hard disks.
Implying, that individual cards access registers on the host system. Socket Services can be added to a computer as aDevice driver, or it can be built into PC BIOS
Immediately, on top of Socket Services in the hierarchy are the Card Services. Card Services is an application programming interface API which permits multiple software programs to work with multiple PCMCIA cards.
For instance, Card Services will allow both internet applications and fax applications to use an installed PCMCIA card modem. Like Socket Services, Card Services can be implemented as a device driver. It can also be built into a computer's operating system, as it is in Microsoft Windows 95/98/NT etc . Specifications PCMCIA specification 2.1 provides for a 16-bit bus interface, has a maximum clock speed of 10 MHz and is capable of speeds to 20 Mbps. The 2.1 spec. does not provide for bus mastering, DMA, or multiple interrupts. While PCMCIA provides only a minimal performance improvement over ISA, and does not come close in speed toPCI, it does provide for considerably more flexibility than either of the others. The two most important features of PCMCIA are its Plug and Play and Hot Swapping capabilities.
As with PCI, PCMCIA cards are truly Plug and Play--you simply insert them, and instructions coded into chips on the card provide the information a host needs to configure the cards and appropriately allocate resources. Not only are there no jumpers or switches to set, users never even see the inside of a PCMCIA card. It is simply inserted into the drive, and the system does the rest. In 1995, the PCMCIA 2.1 specification was enhanced to provide for 32-bit operation. The new architecture, called CardBus, was closely based on the PCI bus, and strove to provide the same improvements over the 16-bit PCMCIA card as PCI did over ISA. As such, CardBus provides for 33 MHz operation and correspondingly increased data transfer. It also introduces DMA and bus mastering to PCMCIA based systems, which can markedly increase performance. Realizing that there are still many 16-bit PCMCIA card peripherals in the marketplace CardBus is fully backward compatible with the older card design. Applications Though PCMCIA card use is not limited to portable computers, there are few instances where it is the best choice for data communication in desktop computers. In desktops, PCMCIA is better suited for adding extra storage space via hard-disk cards, or transferring large files from portable systems. However, for laptop and handheld computers, PCMCIA provides a way to connect a varied array of peripherals to the system, and to share those devices with a desktop computer. Clearly there is a size advantage to PCMCIA for portable applications. The cards are small, light, and have low power requirements. They are an ideal interface choice for peripherals that have been scaled down for portable use. Further, the ability to Hot Swap PCMCIA cards provides for the flexibility needed to use multiple peripherals with only one or two slots.USB and IEEE 1394 provide Hot Swapping are other alternatives for portable applications. IEEE 1394 uses a particularly small cable ideal for portable applications, and is ideal for high speed audio and video applications. However, to use USB or IEEE 1394, the peripheral devices in your system must be replaced with bus specific devices--an expensive prospect. Further, many USB products must be powered by the computer itself, thereby reducing the time a laptop can function on battery alone. Or, if too much power is required, they must be plugged-in, making them less attractive portable solutions. Nevertheless, if cost and power conservation are the primary concerns of the application, PCMCIA is still the best, most flexible choice for portable applications.
[Edit this page] [Page history] [What links here] [Discuss this topic] [Printer Friendly]
