Datasheet
1U Server Chassis SR1300 Hot-Swap SCSI Backplane
Revision 1.2
Intel order number A94544-004
31
The maximum high-level input current at 0.9V
DD
, of both the SDA pin and SCL pin of an I
2
C
device, is 10uA, including the leakage current of a possible output stage.
The maximum capacitance, of both the SDA pin and the SCL pin of an I
2
C device, is 10pf.
6.3.2.3 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
.
6.3.3 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 down the bus; it is
recommended to pulse SAF-TE infrequently. SAF_TE command processing is 2-10ms.
The SYM53C80S supports the following features:
• Supports the American National Standards Institute (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 Mbytes/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
6.3.4 SCSI Interface
The SCSI interface on the SR1300 hot-swap SCSI backplane provides the required circuitry
between the SCSI bus and the 80C652 micro-controller. This allows the micro-controller 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 micro-controller. The 53C80S is a
single-ended, narrow device.
6.3.5 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.