STD Bus Types

Contents

STD Bus Types
STD Z80 and STD 80
STD 32
Compatibility
Making a Choice
For More Information

STD Bus Types

The arrival of the STD 32 Bus specification in 1990 makes it important to distinguish between what are now three STD Bus product types: STD Z80, STD 80 and STD 32. Although there is a great deal of compatibility between the versions, the special properties of each should be kept in mind when designing a system. This section will help identify the differences between, and the appropriate applications for, STD Z80, STD 80 and STD 32 Bus products.

STD Z80 and STD 80
"STD Z80" and "STD 80" are the designations used throughout this catalog to identify products compatible with the original 56-pin STD Bus standard. These products are also known simply as "STD Bus" compatible. STD Z80 and STD 80 specify products which are processor specific functions. STD Z80 refers to products designed to operate with the Z80 family of processors, while STD 80 refers to products for use with the 8088 or 80188 family of processors.

STD Z80 and STD 80 Bus products use a 56-pin backplane, with 0.125" contact spacing, for card interconnection. An 8-bit wide data path is used for all bus transfers.

STD 32
"STD 32" is the designation of the latest version of the STD Bus. Established in 1990, the STD 32 Bus version was created as a growth path for users who require extended addressing, 16 and 32-bit bus transfers, multi-processor operation, multiple DMA channels, and other performance enhancements.

The STD 32 Bus is a carefully designed extension of the familiar STD 80 Bus. As a superset of the STD 80, it is fully backward compatible with STD 80 cards and backplanes. It retains all of the key STD Bus benefits: compact size, high reliability, rugged packaging, and low cost.

STD 32 Bus products use a 136-pin connector pattern for card interconnection. The design retains all of the original STD Bus pins, while interspersing additional signals on .0625 inch spacing. The same connector technology as used in the Micro Channel and PCI bus structures made possible both the increase in density and the improved contact performance of the STD 32 connectors.

The STD 32 Bus provides a 32-bit wide data bus to support 8, 16, and 32-bit data transfers. Dynamic bus sizing, which varies the data path size depending on the requirements of the peripheral card being addressed, gives the STD 32 Bus its tremendous flexibility.

Compatibility
One of the most important features of the STD 80 and STD 32 standards is their compatibility. The STD 32 standard was carefully designed to allow complete backward compatibility with existing STD 80 products.

Its backward compatibility means that all of the existing STD 80 I/O cards are STD 32 compatible. STD 32 users can draw from the extensive selection of existing peripheral cards, and use them freely in STD 32 systems. In addition, many STD 32 cards can be used in STD 80 card cages. High speed STD 32 CPU cards can be used directly with STD 80 backplanes. The new VersaLogic CPU cards automatically sense the STD 80 bus width, and reconfigure themselves to perform 8-bit data transfers. In addition, many STD 32 peripheral boards are designed with a jumper option to facilitate operation in either STD 32 or STD 80 mode.

Making A Choice
Selecting the STD Bus hardware that you will use is obviously an important step in system design. However, the flexibility of the STD Bus makes this choice less critical than it is with other design approaches. In most cases STD Bus systems can be upscaled (for performance) or downscaled (for economy) later in the development cycle if needed.

The most important choice in system design is the processor card. It determines the basic performance level of the system and, to some extent, which software tools can be used for development. Also of importance is the capability of the bus itself. Required bus performance varies greatly with the type of control system being designed.

For More Information

For additional information on STD Bus characteristics, system configurations, or application requirements, please contact VersaLogic's sales or technical support departments by phone at (541) 485-8575 or e-mail at info@VersaLogic.com.

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