SR2300 2U Server Chassis Technical Product Specification
Revision 1.2
Intel Order Number A94546-004
39
6.2.2.3 Noise
Margin
•
Noise margin minimum on the Low level is 0.1 V
DD
•
Noise margin minimum on the High level is 0.2 V
DD
6.2.3
Symbios* SYM53C80S SCSI Controller
The SCSI backplane uses a Symbios SYM53C80S controller to perform all SCSI functions.
Device selection is memory-mapped at address FB00-FC00. It is reset on power-up and when
reset is asserted to the backplane. SYM53C80S access slows the bus, so it is recommended
that SAF-TE be pulsed infrequently. SAF-TE command processing is 2 - 10ms.
The SYM53C80S supports the following features:
•
The ANSI X3.131-1994 standard
•
Parity generation with optional checking
•
No external clock required
•
On-chip 48mA single-ended drivers and receivers
•
Functions in both the target and initiator roles
•
Direct control of all SCSI signals
•
Asynchronous data transfers of up to 5.0 MB/second.
•
Variety of packaging options
•
SCSI protocol efficiency is directly proportional to the speed of the microprocessor
•
CMOS parts provide additional grounding and controlled fall times that reduce noise
generated by SCSI bus switching
•
SCAM Level 1 and 2 compatibility
6.2.4 SCSI
Interface
The SCSI interface on the SR2300 Hot-swap SCSI Backplane provides the required circuitry
between the SCSI bus and the 80C652 microcontroller. This allows the microcontroller to
respond as a SCSI target. The interface consists of a Symbios 53C80S SCSI Interface Chip,
which functions as translator between the SCSI bus and the microcontroller. The 53C80S is a
single-ended, narrow device.
6.2.5
LVD to SE Bridge
Since the 53C80S is a single-ended, narrow device, an Adaptec* AIC-3860 LVD-to-SE
Transceiver (Bridge) is used to create a single-ended extension of the LVD bus. This allows the
53C80S to communicate with the LVD bus.
6.2.6 SCSI
Termination
Passive SE termination is used for the single-ended extension of the SCSI bus on which the
53C80S resides.
LVD/SE multi-mode terminators provide SPI-4 compliant active termination for the backplane
end of the SCSI bus. It is assumed that the other end of the SCSI segment is properly
terminated as required by the SPI-4 specification. Multi-mode termination is implemented on the
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