This primer is intended to help people understand the different SCSI signalling used in Creo’s product lines.
Types of SCSI
Single-Ended SCSI (+5V to ground, 2940UW & 2940U2W, and
all motherboard embedded SCSI controller on DG and DELL 2400L Servers): This
is typically for internal disk or external single DLT tape drive connection.
This is for short connection ONLY, max. 10' total cable length.
Low Voltage Differential (LVD +/-3V Diff.) SCSI (2940U2W
and embedded SCSI controller in DG 2300/3700, and DELL 2400L & 6400 servers):
This signal can be autoswitch to signle-ended signal if the controller detects
single-ended devices connected on the bus. This is getting more and more widely
accepted as standard SCSI signalling today. This signalling is rather new
compared to that of the Differential (sometimes refered as High Voltage Differential
or HVD) and the cable length is longer than SE (I think about 50' or so) and
much better noise immuned than SE. This is used in all DG 2300/3700 and all
DELL servers' internal disks or external single DLT tape drive connection
and some DLT tape library start to appear as LVD device (i.e. ADIC Scalar
100)
Differential SCSI (+/- 5V, 2944UW or 3944AUWD, sometimes
refered as HVD or High Voltage Differential to differentiate it with the LVD
devices mentioned above): There is no server with embeded Diff. SCSI controller,
it is available as PCI card (namely the Adaptec 2944UW and 3944AUWD) ONLY,
it's used to connected to DLT Tape library and Our Platesetter/Trendsetter
output devices. (On the AlphaServers, there's also Qlogic controller used
on alphaserver 2100/ETN30/400, InterServer dual channel on the Digital Server
5300, and the Adaptec 2944UW on the Digital Personal Workstation 1/500a and
the AlphaServer 4000.)
SCSI bus termination
A rule of thumb about SCSI termination is that ONLY the two devices at the two end of the chain need to be terminated, all devices in the middle MUST NOT have
termination turned on. Ensure that the correct type (Single-Ended, LVD or Differential) terminator is installed.
SCSI power up bus negotiation and SCSI Device type and Data Transfer mode:
In a system with external SCSI device connection, rule of thumb is always
power up the device first, then the server so that the device is ready to
reply to the server query for for mode of connection (i.e. Narrow, wide, Ultra
wide, Ultra 2, Ultra 2 Wide, etc.) to whatever mode of connection that the
device is capable of. Although the Workstation s/w (and Print Console) has
implemented a SCSI watchdog to help re-synchronize with the device turned
off and on during service so that workstation does not have to be powered
up and down often during the service period. But it’s still a good practice
to always power up the output device first/ Workstation second, during the
very first power up cycle.
Trendsetter SCSI connection mode is Synchronous Fast Wide (16-bit) SCSI
and Ultra Wide (Maxium 40 MBytes/Sec. burst) ONLY; it will NOT accept Asynchronous
narrow (8-bit) SCSI or Asynchronous wide SCSI transfer mode. Some SCSI controller
(eg. DEC KZPSA controller) do exhibit such behavior as described here.
Trendsetter will identify itself to the workstation as a Printer device.
SCSI data flow between the Workstation and the TS cardcage:
Once all of the above critiria are met, ONLY the Raster data (bitmap, 10101010101....) is passed from the RIP to the SCSI Printer device (through NT SCSI controller driver such
as AIC78xx.SYS for the Adaptec 2944UW controller, to SCSIPRNT.SYS, then to SCSIPORT.SYS out to the wire).
The raster data reach the TS backplane, through the DPE (or now a day FDPE) which buffer the incoming raster data into its two buffers (one buffer being emptied to the laser
head while the other is being filled up) to allow it to be able to continually process data at high speed as long as the Workstation can supply the data at the sustain rate, which:
for the "F" type (Thermal I head) is equal to about 6MB/sec
for the "V" head (or 1.7 times head), the sustain SCSI data rate is approx.
10MB/sec
and the soon to be "V" enhanced, the sustain SCSI data rate is about 11.6MB/sec
Troubleshooting SCSI problem connected to output devices:
Check for physical things that can be visually inspected, SCSI pin bend
in the cable connectors, between intermediate cables (i.e. from the
cardcage backplane to the platesetter connector panel, I’m not sure if
the TS still has the inter-connecting SCSI cable, best if it’s no longer
used).
Ensure the approved SCSI card is installed (i.e. 2944UW/DG for DG server and 2944UW/DELL for DELL server).
Ensure all NT drivers (AIC78xx.SYS, SCSIPRNT.SYS and SCSIPORT.SYS) are started successfully with the correct version, and that the "Creo Platesetter
3244" device appears after the appropriate SCSI controller (i.e. Adaptec AHA290x/291x/294x/394x/4944/AIC78xx PCI SCSI Controller (NT 4.0)) in
Control-Panel’s "SCSI Adapters" applet.
Start up the Workstation software and ensure there's no SCSI error reported from the software console.
Test plot a simple file to a dummy plate to make sure the SCSI sub-system is working fine.
If 1 to 5 is carried out without problem, then plot the problematic file and monitor for error.
