PMC Ultra SCSI 2 PMC SCSI Wide ultra SCSI 2

logo-new.gif (4383 bytes)

PMC SCU2 Wide Ultra 2 SCSI Controller 


A top performance PMC SCSI Controller supporting most flavours of SCSI interface up to Wide Ultra 2 SCSI with a demonstrable transfer rate in excess of 79Mbytes/Sec. The on-board SCSI temination supports both LVD (Low Voltage Differential) and SE (Single Ended) modes of operation automatically and are selected under software control. SCSI bus connection is via the front panel SCSI-2 style connector or via the PMC P4 rear connector.


PMC-SCU2.gif (34720 bytes)

pmcscu2-block.gif (3337 bytes)








Key Features

PCI Features

Connects directly as one load to the PCI bus. 816byte DMA FIFO for improved speed matching. Functions as full 32-bit PCI DMA Bus Master. Complies with PCI 2.1 Specification. Supports 33MHz PCI Bus zero wait state operation. Supports maximum burst transfer rate of 132MBytes/sec. Supports PCI extended access cycles.

SCSI Features

SYM53C895 SCSI Controller

The PMC SCU2 uses a SYM53C895 PCI-to-Ultra2 SCSI I/O Processor, which incorporates Universal Low Voltage Differential (LVD) signalling for SCSI. The SYM53C895 uses LVDlink transceivers, which remove the distance and device constraints in SCSI single-ended designs and offer higher data transfer rates. As compared to Ultra SCSI designs, the SYM53C895 provides twice the performance and allows four times the cable length and number of connected devices.

The SYM53C895 can support up to 12m cables and up to 15 peripheral LVD devices on a wide LVD SCSI bus, with the same cables and connectors defined in the SCSI-3 Parallel Interface ANSI standard. For backward compatibility to existing single-ended devices, the Universal I/O features of LVDlink transceivers allow the chip to switch between LVD and single-ended mode. In single-ended mode, the SYM53C895 performs synchronous data transfers up to Ultra SCSI rates, subject to Ultra SCSI distance and device constraints.

Ultra2 SCSI Support

The performance advantage of Ultra2 SCSI over Fast SCSI-2 and Ultra SCSI is most noticeable in applications that use large block size transfers such as video production and editing, or medical imaging, where large files must be stored or transported. The high SCSI bandwidth of Ultra2 SCSI, and the improvements in distance, connectivity, and reliability, make the SYM53C895 an ideal host connection to a RAID controller. Ultra2 SCSI performance along with the other features in the SYM53C895 make it ideal for these and other demanding applications in the high performance RAID subsystem, workstation, and server markets.

LVD Transceivers

The SYM53C895 has integrated Universal LVDlink transceivers, and uses the Differential Sense (DIFFSENS) signal to detect the bus cabling condition. The universal features of LVDlink transceiver's support single-ended (SE) or low-voltage-differential (LVD) SCSI modes, depending on the type of devices connected to the bus.

SCSI Termination

Active SCSI bus terminators are fitted on the PMC SCU2, which are able to terminate the SCSI bus in either low-voltage-differential (LVD) or single-ended (SE) mode depending on the mode detected.

Normally the terminators are controlled by software, but a switch allows permanent enabling or disabling of the terminators. A 1.5A (max) resettable fuse protects the external termination power line against external short circuits.

FLASH Memory

The PMC SCU2 is fitted with 128Kbytes of FLASH memory using an Am29F010 (90ns) device, which can be programmed (and erased) on board via the SYM53C895 device. It is designed to contain boot code to allow operating system booting via the SCSI interface.


The PMC SCU2 is fitted with 16Kbits of EEPROM using a 24C16 device, which is supplied pre-programmed by BVM.

The contents of the EEPROM are read by the SYM53C895 on coming out of reset and are used to set up the control registers after reset, allowing the following to be set:

Operating Environment

Dimensions:      74.0mm x 149.0mm (single PMC size)
Power:         +5v 230mA typical, +3.3v 140mA typical
Environmental:  0 to 70 C, 95%  humidity non-condensing (extended range to order)


BVM Limited can be contacted by Telephone +44 (0)1489 780144  Fax +44 (0)1489 783589
or email
Copyright 1998-2003 BVM Limited. All rights reserved. All Trademarks acknowledged