PCMCIA 16 bit Bus

 

PC Card
Personal Computer Memory Card International Association

PC Card Description

The PCMCIA [PC Card] specification defines both the Electrical and Physical specifications for a 68 pin interface residing in one of 3 form factors, which differ only in thickness;
Type I: dimensions 3.3mm x 85.6mm x 54.0mm (TxLxW), Version 2.1 allows the length to increase 50mm to 135mm
Type II: dimensions 5.0mm x 85.6mm x 54.0mm (TxLxW), Version 2.1 allows the length to increase 50mm to 135mm
Type III: dimensions 10.5mm x 85.6mm x 54.0mm (Tall x Length x Width)

In most cases cards designed to the PCMCIA specification are used on laptop computers. The smaller size of the PCMCIA card can be used to implement normal desktop expansion boards into a smaller form factor which may be inserted into a notebook computer. PCMCIA cards are commonly used as memory expansion [physical memory, or hard disk drive], modem, or other uses. In some case PCMCIA slots are also provided on desk top computers.

The implementation of this spec based on the ISA bus is termed the PC Card with a 8/16 bit data bus, 26 address lines, and no bus mastering. PC Card-16 cards use an 8-bit or 16-bit interface that operates at ISA bus speeds (10 MHz) using an ISA-like asynchronous protocol. It's called CardBus when implementing the local PCI bus (32 data bits only). All of the PCMCIA implementations use Plug and Play and have Hot Swapping capabilities. The 16-bit PCMCIA 'PC Card' will operate up to a maximum of 20MBps, or 160Mbps. However the actual throughput will depend on the minimum cycle time and the transfer mode [Byte/Word] and will never reach the maximum throughput rates.

Miniature Card is a smaller implementation of PCMCIA. Miniature Cards dimensions 3.5mm x 33mm x 38mm (Tall x Length x Width). The electrical specifications are a subset of the PC Card standard, restricted to memory applications only. It uses a 16-bit data bus and a 24-bit address bus to allow a single card to store up to 64MB.

The PCMCIA 'PC Card' standard [discussed on this page] should not be used as an up-grade because it's based on the slower ISA bus standard. Use the Cardbus standard of PCMCIA instead, which is based on the PCI bus specification. The PCI implementation in Cardbus is much faster, and a newer bus standard. I've heard that version 2 [1991] of the PCMCIA standard was not widely followed or was not well defined. Version 2.1 [1993] addressed some of the standards issues, but may still have issues with standardization. The PCMCIA 'PC Card' bus is obsolete, and should not be used for new designs. At a minimum use the PCI version of the bus discussed above. Removable memory cards are produced in a number of different formats

PC Card, Pin Out

The table provides the pin out for the 16-bit PC Card.

PCMCIA 68-pin Connector Pin Out And Signal NamesPin #Signal NamePin #Signal NamePin #Signal NamePin #Signal NamePin #Signal Name1Ground15WE29A043VS1/RFSH57VS2/RFU2D316Ready30D044Reserved58Reset3D417Vcc31D145Reserved59Wait4D518Vpp132D246A1760Reserved5D619A1633Wp47A1861Reg6D720A1534GND48A1962BVD27CE121A1235GND49A2063BVD18A1022A736CD150A2164D89OE23A637D1151Vcc65D910A1124A538D1252Vpp266D1011A925A439D1353A2267CD212A826A340D1454A2368GND13A1327A241D1555A24-----14A1428A142CE256A25-----