Sun Microsystems 60 service manual Host Adapter, Figure C-10Configuration for the Scsi Bus

FIGURE C-10

C.1.14 SCSI

The system unit implements a small computer system interface (SCSI) Fast-20 (UltraSCSI) parallel interface bus. The UltraSCSI provides the following:

■Efficient peer-to-peer I/O bus devices.

■Mechanical, electrical, and timing specification definition that support transfer rates of 20 or 40 Mbytes per second (corresponding to the data path width of an 8-bit, or 16-bit bus, respectively).

■Peak bandwidth of 40 Mbytes per second (with implemented 16-bit bus width).

The internal SCSI bus is terminated at each end. One set of terminators is located close to the CD-ROM drive connector on the CD-ROM SCSI card. A second set of

terminators is located close to the 68-pin external SCSI connector.shows the SCSI bus configuration.

CD-ROM	Disk 1
drive
	(UltraSCSI)
(8-bit)

T SCSI bus

Disk 0				Host
			adapter
(UltraSCSI)
		(UltraSCSI)
	T				T

External devices (UltraSCSI)

SCSI bus

Internal SCSI bus External to chassis

FIGURE C-10Configuration for the SCSI Bus

C.1.14.1 Host Adapter

The host adapter is a Symbios Logic PCI-SCSI I/O processor IC. The host adapter and all target devices comply with the Fast-20 single-ended drivers and receivers characteristics. The electrical characteristics of the output buffers include:

■Vol (output low) equals 0 to 0.5 Vdc with Iol at 48 mA (signal asserted)

■Voh (out high) equals 2.5 to 3.7 Vdc (signal negated)

■trise (rising slew rate) equals 520 mV per nanosecond maximum (0.7 to 2.3 Vdc)

■tfall (falling slew rate) equals 520 mV per nanosecond maximum (2.3 to 0.7 Vdc)

C-30Sun Ultra 60 Service Manual • August 2001