Srnall Colnputer Systems Interface - HP 340 Series Service Manual

Small Computer Systems Interface
SCSI Identification
The SCSI is identified by this message:
HP98265 (SCSI S 16) at 14
If two SCSI devices are listed at the same bus address, the SPU will stop. To correct this, make
sure each SCSI device has its own unique address.
If all SCSI addresses are listed for the same device, change the address on the device to an
other address other than 7. Address 7 is the SCSI interface and must not be used as a SCSI
peripheral address.
SCSI Testing
There are two levels of SCSI testing: normal and extended.
Normal testing is done at powerup or if the Boot ROM is in LOOPING test mode. This test
only checks the general functionality of various registers on the interface. It will only detect
gross failures.
The identification line Inay be followed by one of these error messages:
register test failed
fuse burned out
If any of these messages appear, no attempt will be Inade to use the interface as a boot source.
The "fuse" is an electronic fuse which can be reset by either pressing
I
Reset
I
to cause the boot
rOln to restart or by cycling power to the SPU.
Extended testing includes three parts:
• Register test (as done in normal testing).
This test is always run and if it fails, the remaining sections will be skipped .
• Loopback test.
This test displays these messages in the order listed and the indicated actions are required:
Turn OFF ALL SCSI devices,
which means to turn off power to ALL SCSI peripherals. If
a particular sequence is required for proper system shut-down, that sequence must be
followed.
Disconnect cable at nearest device,
meaning remove the SCSI cable at the first SCSI
peripheral down the SCSI interface froln the SPU.
X cancels
J
RETURN continues testing,
wherein pressing IT] cancels the test or
I
Return
I
continues the SCSI test.
This test checks transmit and receive functionality both with and without DMA interac-
tion. If this test fails, cable test can still be executed. If the user cancels testing at this
point by typing [KJ in response to the prompt, this section and the following sections are
skipped. It will take a second or so with bit-mapped video circuits to clear the display.
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Boot ROM Functions