PCMCIA bus interface cards translate the data from the PCMCIA bus to another bus, and vice versa. They are used to connect two otherwise incompatible buses. PCMCIA is an acronym for the Personal Computer Memory Card Association, the organization which develops and maintains standards for PCMCIA cards. Originally, these devices were known as PC cards because they were designed to add memory to portable computers. As PCMCIA standards and technologies evolved, however, PCMCIA cards were added to many types of devices. Today, specifications for PCMCIA bus interface cards include bus types, performance, and power requirements along with technology standards and form factors.
PCMCIA bus interface cards are used with many different bus types. Examples include universal serial bus (USB), small computer systems interface (SCSI), general-purpose interface bus (GPIB), IEEE 1394 or FireWire® (Apple Computer), PC/104, parallel interfaces, and CompactFlash® (CompactFlash Association). Typically, the PCMCIA bus connects to the host computer through the PCMCIA slot on one end. On the other end, the device provides a bus or port to the host. For example, a PCMCIA-to-USB adapter converts any computer with a PCMCIA slot into one with a USB port ready to connect peripherals that are USB-supported.
There are several major technology standards for PCMCIA bus interface cards. PC Card Standard 95 is the PCMCIA’s original device standard. It has a 68-pin interface with 16 bits of address and data. CardBus technology runs at 33 MHz and is for cards with 32 bits of address and data. Miniature card technology products are about one-fourth the size of PC Card Standard 95. These PCMCIA bus interface cards use StrataFlash® (Numonyx B.V.) technology, a multilevel cellular architecture; and µBGA, a type of ball grid array. CompactFlash, SmartMedia, and CardBay cards are also available.
PCMCIA bus interface cards are categorized by form factor. Type I cards are 54 mm x 85.4 mm, and can be up to 3.3 mm thick. Type II cards are 54 mm x 85.4 mm, and can be up to 5.5 mm thick. Type III cards are 54 mm x 85.4 mm, and can be up to 10.5 mm thick. Type IV cards have not yet been ratified by the PCMCIA consortium; however, their size is expected to be 54 mm x 85.4 mm with a thickness of 18 mm. Additional form factors for PCMCIA bus interface cards include SmartMedia Card, CompactFlash, Miniature Card, Solid State Floppy Disk (SSFDC), and MultiMediaCard (MMC).