Chart 13. 02/88, Dsp External Sram Failure U414; Chart 14. 02/84, Dsp External Sram Failure U403 - Motorola ASTRO Digital Saber Service Manual

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
Check for
ADSIC
Yes
No
Connections
Repair opens. programming
good?
checksum
error.
Refer to
ADSIC
section on Yes
checksum
FAIL 02/A0.
Chart C.11 error?
During power-up
verify operation
Inputs to
Yes of U415 by
U415
Replace U415.
looking for
functional?
transitions on
inputs IN_B and
IN_A.
No
Replace U405.
Chart 13 . 02/88, DSP External SRAM Failure U414
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.
3) Open in supply or ground to
the IC.
4) Failure of the IC.
During power
up Self-Test
verify E1~ on
No
U414 is enabled
by high to low
transitions of
Replace U414.
R3SEL*.
No
R3SEL* Do all three
Yes
No
SRAMs
appears
exhibit a
functional?
fault?
Yes
Replace U405.
MAEPF-24410-A
Fail 02/84
DSP SRAM U403
Failure
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U403 Source
D0-D23 U405
A0-A12 U405
WR*,RD* U405
E1* U405-A15
E2 U406-RSEL
X/Y*,V/S* GND
VCC +5V
VSS GND
No
Connections
Repair opens.
good?
Yes
Check for
ADSIC
programming
checksum
error.
During power
up Self-Test
verify E2 on
Refer to ADSIC
No
Yes
U403 is enabled
section on
checksum
FAIL 02/A0. by low to high
error?
Chart C.11
transitions of
RSEL.
RSEL
No
Replace
appears
U406.
functional?
Chart 14 . 02/84, DSP External SRAM Failure U403
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.
Besides utiling decoding logic
from the DSP (U405), U403
has additional logic in the form
of RSEL from the ADSIC
(U406). A problem with the
ADSIC in the form of a
programming or hardware fault
will cause a problem with the
operation of this part. Basic
failure modes are as follows:
1) Some problem exists
(open/shorts) with the
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.
3) 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.
4) Open in supply or ground to
the IC.
5) Failure of the IC.
Do all three
No
Yes
Replace U403.
SRAMs
exhibit a
fault?
Yes
Replace U405.
MAEPF-24409-B
10-9