Technical Manual

10-16
Chart 14. 02/90, General DSP Hardware Failure
Fail 02/90
DSP Hardware
Failure
Verify standard
bias per table
Table 3.
No
Isolate and
repair problem.
See Chart C.5
Yes
Standard
bias OK?.
Reflash DSP
code.
Unable to
Reflash
DSP code?
Fail
02/90
persists?
Verify Host Port:
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U405 Source
H0-H7 U701
HA0-HA2 U701
HR/W* U701
HEN* U701
RESET
HREQ*
U701
U701
On power up, verify
transitions on HEN* from
high to low indicating DSP
is being selected.
Synopsis
On power-up the host µC sends
several handshake commands
through the host interface to
the DSP system to coordinate
the power up programming of
the ADSIC and detect any DSP
power up status messages..
This error indicates the host
never received a response
from the DSP. The power up
code is downloaded from U404
and executed internally in the
DSP. This is a wide ranging
problem which may be difficult
to isolate without special tools.
Some basic failure modes:
1) Some fundamental system
clocks or supplies are not
operational.
2) Improper operation of the
ADSIC memory mapping
functions.
3) Corrupted DSP FLASH
program code.
4) Hardware problem with host
µC/DSP interface.
5) Improper configuration of
MODA and MODB by ADSIC.
6) DSP_RST* not operating
correctly.
7) ADSIC not functional due to
missing 2.4MHz reference.
8) Short or open on DSP
address/data bus.
Yes
No
No
Yes
End.
Verify D23 is
pulled high
through R410
at power up.
Replace U405.
D23 is
high?
Yes
No
Repair problem
with R410.
FLASH
programming
error
generated?
No
Yes
At power up
verify state of
MOD select
pins on DSP
when RESET
goes high:
MODA High
MODB Low.
MOD pins
correct?
Yes
No
Verfiy
operation and
continuity of
RSTx on U406.
On power up,
Signal should
transition
from low to
high.
ADSIC RESET
functional?
Replace U701.
No
Yes
Verify 2.4
MHz reference
on U406-IDC
per Fig W10.
*Note
frequency may
be off, if
sequence was
aborted before
ABACUS was
programmed.
Reference
present?
Yes
MAEPF-26028-O
No
Replace U406.
Verify
operation of
ABACUS IC
and repair as
necessary.
Host port
operation
verfied?
Repair opens
as necessary.
No activity
exists on
pins when
measured on
U701 at power
up may
indicate a bad
µC. If this is
the case
replace U701.
Replace U405.
Yes
No
Use ohmmeter to
electrically verify signal
connections to source
IC as shown in sections
on Fail 02/81 and Fail
02/88. If failure still
occurs, then refer to
section on DSP ROM
failure (Fail 02/81).
Chart C.12.