Specifications

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Ampro SCSI/BIOS
To make it easy to use SCSI devices and functions not supported by the standard Ampro drivers
and utilities, functions have been included in the board's ROM-BIOS which allow the use of the
SCSI interface without the need for direct hardware programming. This support is accessed
through an extension of the INT13 ROM-BIOS support, and is known as the Ampro SCSI/BIOS.
The Ampro SCSI/BIOS adds an additional layer of standardization to SCSI, by providing a high
level interface for software that eliminates the need for direct programming of the SCSI bus
interface hardware. This standard software interface is accomplished through an extension to the
INT13 support normally provided in a PC or AT ROM-BIOS for hard disk access. SCSI drivers
and utilities written around the Ampro SCSI/BIOS INT13 extensions will run on any system in
which the INT13 extensions are available. (This includes all of Ampro's DOS compatible Little
Board single board systems.)
Detailed information on the SCSI/BIOS functions provided within the Little Board/286 ROM-
BIOS is available in application note AAN-8804, available from Ampro.
A SCSI/BIOS disable option is provided within the board's configuration EEPROM parameters. It
serves to eliminate the SCSI services within the ROM-BIOS. With the SCSI/BIOS disabled, you
can still use the AIC-6250 device from your software.
If you plan to support SCSI devices using the SCSI/BIOS, you will probably need to become
acquainted with the SCSI bus and its protocols. To obtain a copy of the ANSI SCSI specification,
contact the American National Standards Institute referred to previously in this chapter.
Non-SCSI Programmed I/O
When not needed for standard SCSI functions, this interface can be employed as a programmable
I/O port. In these non-SCSI applications, the AIC-6250's inputs (from the SCSI connector)
provide Schmitt trigger input conditioning, and the outputs (to the SCSI connector) provide open
collector drivers capable of sinking 48 mA, and which may be enabled and disabled under
software control.
Not all of the SCSI bus interface signals can be used in non-SCSI applications, as the AIC-6250
was intended for SCSI specific use. Sixteen of the SCSI bus signals can be used simultaneously
as inputs; of these, a maximum of nine can simultaneously be used for bidirectional I/O. The
available SCSI port output signals can be "bit banged" to generate a wide variety of signal uses
and timings; it is even possible to connect the SCSI port to optically isolated AC and DC input and
output modules, or to a number of off-the-shelf data acquisition and control interfaces.
Information on how to use the Little Board/286 AIC-6250 SCSI interface for non-SCSI
programmed I/O is provided by application notes AAN-8901 and AAN-8801, available from
Ampro.
Note
You cannot use the board's SCSI interface in this manner if it
is also being used for normal SCSI functions.