Motorola ASTRO Digital Spectra Plus Detailed Service Manual page 230

5-12
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.
Refer to
ADSIC
No
Yes
section on
checksum
Fail 02/A0.
error?
Chart C.11
Yes
Refer to a
Fail 02/84.
Chart C.15 02/82, DSP External SRAM Failure U402
September 5, 2008
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.
Due to the
possibility of a
failure causing
a RAM overlap,
U403 should be
verified.
Do all three
Does a fault
No No
SRAMs
exist with
Replace U402.
exhibit a
U403?
fault?
Yes
Replace U405.
MAEPF-24408-B
Fail 02/90
DSP Hardware
Synopsis
Failure
On power-up the host C 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
Isolate and
and executed internally in the
No Standard
repair problem.
DSP. This is a wide ranging
bias OK?.
See Chart C.5
problem which may be difficult
to isolate without special tools.
Some basic failure modes:
Yes 1) Some fundamental system
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
Fail Unable to C/DSP interface.
No No
02/90 Reflash 5) Improper configuration of
End.
persists? DSP code? MODA and MODB by ADSIC.
6) DSP_RST* not operating
correctly.
7) ADSIC not functional due to
Yes Yes
missing 2.4MHz reference.
Verify D23 is
pulled high
FLASH
through R404 At power up
No
programming
at power up. error verify state of
generated?
MOD select
pins on DSP
when RESET
Yes goes high:
MODA High
No
Repair problem D23 is
MODB Low.
Refer to
with R404.
high?
section on DSP
ROM failure
(Fail 02/81).
Chart C.12
Yes
No
MOD pins
Replace U405.
correct?
Yes
Verify Host Port:
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U405 Source
H0-H7 U204
HA0-HA2 U204
HR/W* U204
HEN* U204
RESET U204
On power up, verify
transitions on HEN* from
high to low indicating DSP
is being selected.
Repair opens
as necessary.
No activity
exists on
Host port
No
pins when
operation
measured on
verified?
U204 at power
up may
indicate a bad
Yes
C. If this is
the case
replace U204.
Replace U405.
Chart C.16 02/90, General DSP Hardware Failure
Troubleshooting Charts
Verify
operation and
continuity of
RSTx on U406.
On power up,
signal should
transition
from low to
high.
No
ADSIC RESET
Replace U204.
functional?
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.
Yes
Reference
Replace U406.
present?
No
Verify
operation of
ABACUS IC
and repair as
necessary.
MAEPF-24414-B
6881076C25-E