10-12
Reference
Information
Portable
PLUS
Computer
EPROM Diagnostic Test Function. The diagnostic EPROM
is
located in the first 16K bytes of plug-in
ROM (addresses 90000 through 93FFF). When the module is connected to the computer, the scope
routines are run at power-up.
EPROM Burner Function. The configuration EPROM in the HP Portable PLUS Computer has in-
formation that
is
unique to the unit (such as the serial number). When a configuration EPROM is bad,
the diagnostic module
is
used to burn another EPROM.
To
burn
an
EPROM, the diagnostic module
must be plugged into the
left port, a
25
Vdc
power supply connected to
J2,
and
the EPROM-burner
program must
be
loaded into the computer's
RAM.
Data sent
to
the diagnostic module determines whether the EPROM is
to
perform a "read"
or
"write"
operation, controls the burn-in voltage,
and
enables the burn duration (one-shot) timer.
Checking the EPROM Burner. Run the
DMTEST
program on the service diagnostic disc.
Select the test to be performed by pressing the appropriate function key
on
the display:
1. Calibrate the EPROM timer.
2.
Test the diagnostic module switches.
3.
Check the diagnostic module EPROM code.
Test 1. Set the EPROM programmer timer.
This test allows you
to
calibrate
and/or
check the
51
ms timer pulse generated by the diagnostic
module (for burning
EPROMs):
Press
the
CIT)
function key
to
run this test.
Set the scope for 1
V /division
and
10 ms/division. Probe UI8, pin 6
and
look for pulses
at
51-ms
intervals.
If
the pulses are not
51
ms apart, adjust
R14
until the pulse duration
is
correct.
If
no
pulses
are present, check
U18, pin 3 for a 5-MHz clock signal
and
U18, pin 2 for a
5I-ms
pulse.
If
either
signal
is
missing, check UI7.
To
exit this test, press
and
hold down the
CID
contrast
key.
Test 2. Diagnostic module switch tests.
These tests toggle the
EPROM programmer control registers:
Press the @ function key to run these tests.
Probe Xl, pin
28
(EPROM socket)
and
look for the voltage to switch between 0
and
5 Vdc. (This turns
Vcc
to the EPROM
on
and
off.)
If
this voltage does
not
toggle, check UI4, pin 3 for toggling. Also
check that the signals at
UI4, pins 4
and
5 do not change.
Press
any
key to proceed to the next switch test.
Probe Xl, pin 1 (EPROM socket)
and
look for the signal to switch between 5
and
21
Vdc. (This turns
the
Vpp EPROM programming voltage on
and
off.)
If
this signal does
not
switch, check the
21
Vdc
regulator VRl. Also check that UI4, pin 4 is switching between 0
and
5Vdc,
and
that U14, pins 3
and
5 do not change states.
Press
any
key to proceed
to
the next switch test.
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