Specifications

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Internally, pins 2-7 of the SIP networks have 220 ohm resistors connected to +5 volts (pin 8), and
330 ohm resistors connected to ground (pin 1).
Note that the SCSI Bus termination networks consume significant power (.8 watt). If power
consumption is critical, consider having the bus termination external to the board, and externally
powered.
External Termination Power Option
The SCSI specification includes the option of using external bus termination. To accommodate
this feature, the Little Board/286 provides a jumper option (W1), which allows the board to
supply termination power (+5V) to the SCSI bus TERMPWR signal (pin 26). A Shottky
protection diode is included on the board, as recommended by the ANSI specification, to prevent
board damage from current which might otherwise flow from the SCSI bus.
The default jumpering of this option is unshorted; i.e. termination power is not normally supplied
by the Little Board/286.
SCSI Controller Interrupt
Jumper W2, when shorted, connects the board's SCSI interface controller interrupt output signal
to interrupt IRQ15 on the AT bus. Though not currently used, the IRQ15 interrupt is reserved for
future enhancements of the Ampro SCSI/BIOS. It is recommended that you not use it in your
system designs, to preserve compatibility with future Ampro BIOS revisions. Therefore, leave
jumper W2 in its factory setting (shorted or unshorted).
"Soft Configuration" Options
Every SCSI device must be configured for a specific SCSI bus ID, between 0 and 7. The SCSI
Initiator ID of the Little Board/286 is determined by a parameter stored in the board's
Configuration Memory. Use the Ampro SETUP utility to set this value. Normally, the board's
SCSI "initiator" ID should be set to 7, and the ID's of the disk drives and other SCSI "target"
devices should be set to 0, 1, etc.
Another important SCSI-related option, available via a parameter stored in the Configuration
Memory, is whether or not the SCSI/BIOS services in the board's ROM-BIOS are desired. Using
the Ampro SETUP utility, you can disable or enable SCSI/BIOS services. If you set the
parameter to disable the SCSI/BIOS services, there will be no support BIOS support for it at all.
This might be desirable for several reasons:
n To speed system booting when normal SCSI interfacing is not required, such as in a
floppy-only system. Otherwise, there is a delay during system booting, while the system
waits to see if a SCSI device at ID0 LUN0 becomes ready.
n To disallow SCSI/BIOS control of the SCSI hardware, when the interface is to be used in a
non-standard manner.
n When using an AT hard disk controller (on the bus, or connected by means of the
MiniModule/ATDisk controller interface) instead of using a SCSI device.