Chart 15. 02/82, Dsp External Sram Failure U402; Chart 16. 02/90, General Dsp Hardware Failure - Motorola ASTRO Digital Saber Service Manual

Fail 02/82
DSP SRAM U402
Failure
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U402 Source
D0-D23 U405
A0-A12 U405
WR*,RD* U405
E1* U405-A15
E2 U405-A13
X/Y*,V/S* GND
VCC +5V
VSS GND
No
Connections
Repair opens.
good?
Yes
Check for
ADSIC
programming
checksum
error.
Due to the
possibilityof a
Refer to
ADSIC
No
Yes failure causing
section on
checksum
a RAM overlap
Fail 02/A0.
error?
Chart C.11 U403 should be
verified.
Yes Does a fault
Refer to a
exist with
Fail 02/84.
U403?
Chart 15 . 02/82, DSP External SRAM Failure U402
Synopsis
On power up the DSP writes
data to the device and then
verifies the data. This failure
indicates the DSP SRAM failed
this pattern/checksum test.
U402 decoding logic consists
entirely of address lines from
the DSP (U405). A failure in
this part would point to the
part itself or with the DSP.
However the possibility exists
for a decoding logic problem to
cause one of the other SRAMs
to overwrite U402. This is
particularly the case with
U403 which is selected with
the RSEL signal from ADSIC
(U406). This problem should
be investigated before
replacing any parts. Basic
failure modes are as follows:
1) Some problem exists
(open/shorts) with the
external address/data bus.
2) Possible failure of the DSP
address/data bus or
RD*/WR*/PS*/DS* signals
used in selecting this part.
Since the other two DSP
SRAMs share this bus as well
as other ICs, this is not a likely
failure.
3) Open in supply or ground to
the IC.
4) Failure of the IC.
No Do all three
No
SRAMs
Replace U402.
exhibit a
fault?
Yes
Replace U405.
MAEPF-24408-B
Isolate and
repair problem.
See Chart C.5
Fail
No
02/90
End.
persists?
Yes
Verify D23 is
pulled high
through R404
at power up..
No
Repair problem D23 is
with R404. high?
Yes
Replace U405.
Repair opens
as necessary.
No activity
exists on
pins when
measured on
U204 at power
up may
indicate a bad
µC. If this is
the case
replace U204.
Chart 16 . 02/90, General DSP Hardware Failure
10-10
Fail 02/90
DSP Hardware
Synopsis
Failure On power-up the host µC sends
several handshake commands
through the host interface to
the DSP system to coordinate
Verify standard
the power up programming of
bias per table
the ADSIC and detect any DSP
Table 3.
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
No Standard
DSP. This is a wide ranging
bias OK?.
problem which may be difficult
to isolate without special tools.
Some basic failure modes:
1) Some fundamental system
Yes
clocks or supplies are not
operational.
Reflash DSP
2) Improper operation of the
code.
ADSIC memory mapping
functions.
3) Corrupted DSP FLASH
program code.
4) Hardware problem with host
µC/DSP interface.
Unable to
No
Reflash 5) Improper configuration of
DSP code? MODA and MODB by ADSIC.
6) DSP_RST* not operating
correctly.
7) ADSIC not functional due to
Yes
missing 2.4MHz reference.
FLASH
At power up
programming No
error verify state of
generated?
MOD select
pins on DSP
when RESET
Yes goes high:
MODA High
MODB Low.
Refer to
section on DSP
ROM failure
(Fail 02/81).
Chart C.12
Verfiy
operation and
No
MOD pins continuity of
correct? RSTx on U406.
On power up,
Signal should
transition
Yes from low to
high.
Verify Host Port:
Use ohmmeter to
electrically verify No
ADSIC RESET
Replace U204.
following signal connections
functional?
to source IC:
Signal @ U405 Source
H0-H7 U204
HA0-HA2 U204
Yes
HR/W* U204
HEN* U204
Verify 2.4
RESET U204
MHz reference
on U406-IDC
On power up, verify
per Fig W10.
transitions on HEN* from
*Note
high to low indicating DSP
frequency may
is being selected.
be off, if
sequence was
aborted before
ABACUS was
programmed.
Host port
No
operation
verfied?
Yes
Reference
Replace U406.
Yes
present?
Replace U405.
No
Verify
operation of
ABACUS IC
and repair as
necessary.
MAEPF-24414-A