Adaptec SlimSCSI APA-1460, Техническое описание

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APA-1460 SlimSCSI Technical Reference
Stock Number: 510671-00, Rev. A
Page: 3-4
Print Spec Number: 492966-00, Rev. A
Current Date: 8/22/94
ECN Date: 8/30/94
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APA-1460 SlimSCSI Technical Reference
Termination Power
No external termination power is provided in this design.
Internal Bus Pull-up Resistor
There are eight 100 K-ohm pull-up resistors in D0-D7 line, to ensure software compatibil-
ity. The
aspi2dos initialization routine will check Port A and Port B status of the AIC-6360
chip in order to decide which host adapter or what options to choose (parity checking,
Fast SCSI etc.). In this case, because there are no jumpers inside the APA-1460 Card,
aspi2dos must get an FFh to recognize and configure this Card properly. The pull-up
resistors ensure the FFh status.
Cable Specifications
You can connect up to seven external SCSI devices to the APA-1460. The APA-1460 comes
with either a high-density or low-density 50-pin SCSI-2 compatible connector on the
Cable. To connect more than one device, daisy-chain the additional devices to the first
SCSI device.
Note:
The APA-1460 supports only single-ended SCSI devices. Differential SCSI
devices may be damaged if connected to the host adapter bus. Most SCSI devices
currently produced are single-ended SCSI devices. Consult you SCSI device
documentation.
When the SCSI bus contains a Fast SCSI host adapter, such as the APA-1460, and one or
more Fast SCSI device, the total length of all SCSI cables connected to the SCSI bus,
including the APA-1460 Cable, must not exceed 3 meters (9.8 feet) to ensure reliable oper-
ation. If no Fast SCSI devices are connected, the total length of all cables must not exceed
6 meters (19.7 feet). See your device documentation to determine if it is a Fast SCSI device.
Make sure your external SCSI cables are of high quality and adhere to the SCSI specifica-
tion. The SCSI specification requires external device cables to be constructed of 50 wires in
25 twisted pairs (signal pairs), with a characteristic impedance of no less than 90 ohms
(90 to 105 ohm recommended).
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