INTEL iSBX-351
SERIAL MULTIMODULE™ BOARD

General Description
Documents
Electronic Diagrams
Multimodule

General description

The iSBX 351 Serial Multimodule Board is a member of Intel’s growing line of expansion Multimodule boards designed to augment the iSBC microcomputers. The Multimodule board provides for expansion of the system serial communications capability by adding one complete, independent, synchronous/asynchronous, RS232C and RS422/RS449 compatible, serial communications channel.

The Multimodule board is designed to be plugged onto a host iSBC microcomputer to provide
an additional serail I/O interface capability. The Multimodule board contains an 8251A USART (Universal Synchronous Asynchronous Receiver-Transmitter) device to handle RS232C or RS422 compatible serial I/O communication schemes. The board also holds an 8253 PIT (Programmable Interval Timer) device that controls frequency and timing functions generated from an on-board 8224 Clock Generator. Baud rates, data formats, and interrupts are jumper and program selectable on the Multimodule board. When operating as an RS232C interface, the Multimodule board requires +5V, -12V, and +12V power. However, as an RS422 interface, only +5V power is required.

The serial I/O port is fully RS232C and RS422/449 compatible; the Multimodule board is electrically compatible with RS422, and mechanically compatible with RS449. Serial communication is implemented with an 8251A USART that may be programmed for operation in most synchronous or asynchronous serial data transmission formats. The serial I/O port
features full- or half-duplex, buffered, transmit and receive capability.

An RS422/449 application of the Multimodule board allows operation in a full- or half-duplex multidrop configuration, in which several iSBX-351 Serial Multimodule Boards share the same two-wire data line. This requires that the user exert software control over each slaves’ output to the data line.

The programmable interval timer provides three separate time/rate clocks, two of which are available for off-board timing and synchronization. The third clock provides timing for the receive and transmit circuitry on the 8251A USART.

The Multimodule board may be wired to generate interrupt requests continuously at a clock rate or on request from the 8251A USART. Interrupt priority is determined on the host iSBC microcomputer.

Electronic diagrams

The iSBX MULTIMODULE System

The iSBX bus is a unique interface facilitating onboard expansion with iSBX Multimodule boards. The iSBX bus is derived directly from the on-board CPU bus and, as such, an iSBX Multimodule board plugged into the iSBX bus becomes an integral element of the single board computer. The physical interface between the single board computer and the iSBX Multimodule board is a unique connector designed specifically for the iSBX bus. The iSBX bus is brought out to a female iSBX bus connector on the single board computer and mates with its male equivalent resident on the iSBX Multimodule board.
The iSBX Multimodule board concept offers a unique design approach to board level users. To date, the designer has had a broad range of single board computers and expansion boards joined together on the Multibus interface. The iSBX Multimodule boards bring a new concept to expansion, providing a product family of smaller modules that can be plugged directly onto the single board computer. These boards come in two sizes. The single wide board is 3.70 inches long and the double wide board is 7.50 inches long. In short, the user may now tailor his application directly onboard the single board computer at a minimal cost. In addition, the iSBX Multimodule boards offer maximum 8-bit performance because it is tightly coupled to the microprocessor through the iSBX bus.
The iSBX bus concept can be expanded to 8/16-bit I/O operations by simply adding 8 data lines and redefining the chip select lines. Both the 8- and 16-bit iSBX Multimodule boards will operate on a 16-bit base board. Physically, the mounting holes on both the 8- and 16-bit iSBX Multimodule boards are identical. The 8-bit iSBX Multimodule connector is a subset of the 16-bit iSBX Multimodule connector. An 8-bit iSBX Multimodule board operating on a 16-bit base board will do all I/O operations with the lower data byte (DATO-DAT’7).
The iSBX Multimodule board specifications are defined in a similar way an I/O component would be.