Dsp External Sram Failure U414 - Motorola ASTRO Digital Spectra Plus Service Manual

Troubleshooting Charts
Fail 02/88
DSP SRAM U414
Failure
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U414 Source
D0-D23 U405
A0-A12 U405
WR*,RD* U405
E1* U415-OUT
E2 U406-A15
X/Y*,V/S* GND
VCC +5V
VSS GND
Signal @ U415 Source
IN_A U405-A14
IN_B U405-A13
Yes
No
Connections
Repair opens.
good?
Refer to
Yes
section on
FAIL 02/A0.
Chart C.11
During power-up
verify operation
Inputs to
Yes
U415
Replace U415.
functional?
inputs IN_B and
No
Replace U405.
Chart C.13 02/88, DSP External SRAM Failure U414
6881076C25-D
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.
U414 is selected by the DSP
(U405) address bus with the
addition of the OR logic gate
U415. 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) Operational failure of the OR
logic of gate U415.
4) Open in supply or ground to
the IC.
Check for
5) Failure of the IC.
ADSIC
programming
checksum
error.
During power
up Self-Test
verify E1~ on
ADSIC
No
U414 is enabled
checksum
by high to low
error?
transitions of
Replace U414.
R3SEL*.
Do all three
R3SEL*
Yes
of U415 by No
SRAMs
appears
looking for
functional? exhibit a
transitions on
fault?
IN_A.
Replace U405.
Repair opens.
Refer to
section on
FAIL 02/A0.
Chart C.11
No
Yes
MAEPF-24410-B
Fail 02/84
DSP SRAM U403
On power-up the DSP writes
Failure
data to the device and then
verifies the data. This failure
indicates the DSP SRAM failed
this pattern/checksum test.
Use ohmmeter to
Besides utilizing decoding logic
electrically verify
from the DSP (U405), U403
following signal connections
has additional logic in the form
to source IC:
of RSEL from the ADSIC
Signal @ U403 Source
(U406). A problem with the
D0-D23 U405
ADSIC in the form of a
A0-A12 U405
programming or hardware fault
WR*,RD* U405
will cause a problem with the
E1* U405-A15
operation of this part.
E2 U406-RSEL
failure modes are as follows:
X/Y*,V/S* GND
1) Some problem exists
VCC +5V
(open/shorts) with the
VSS GND
external address/data bus.
2) Some problem exists with
the ADSIC memory select
(RSEL) which may include an
ADSIC programming problem
(SPI bus) or possibly a failed
ADSIC.
No
Connections
3) Possible failure of the DSP
good?
address/data bus or
RD*/WR*/PS*/DS* signals
used in selecting this part.
Yes
Since the other two DSP
SRAMs share this bus as well
Check for
as other ICs, this is not a likely
ADSIC
failure.
programming
4) Open in supply or ground to
checksum
the IC.
error.
5) Failure of the IC.
During power
up Self-Test
verify E2 on
ADSIC
No
Yes
U403 is enabled
checksum
by low to high
error?
transitions of
RSEL.
RSEL
Do all three
Yes
No
Replace
appears
U406.
functional?
exhibit a
Replace U405.
Chart C.14 02/84, DSP External SRAM Failure U403
5-11
Synopsis
Basic
No
Replace U403.
SRAMs
fault?
Yes
MAEPF-24409-B
October 28, 2002