Technical Manual

10-11
Chart 9. 01/88 MCU (Host µC) External SRAM
Fail 01/88
Host µC External RAM
Failure.
Verify standard
bias per table
Table 3 pertaining
to host µC.
No
Isolate and
repair problem.
Yes
Standard
bias OK?.
Signal @ U702 Source
OE* U701
WE* U701
HD0-HD7 U701
4XECLK U701
HA0-HA4,
HA14_IN, HA15_IN,
HA16,HA17 U701
CSIO1* U701
CSPROG* U701
Verify Host RAM:
Use ohmmeter to
electrically verify
following signal connections
to source IC:
Signal @ U705 Source
HA0-HA13 U702
HD0-HD7 U701
MEMR/W* U702
OE* U702
CS* U708
Signal @ U211 Source
IN_B U701
IN_A U702
Synopsis
This failure indicates a failure
in the µC external SRAM at
power up test. Some basic
failure modes:
1) Missing supply or ground to
SLIC.
2) Open in parallel address bus,
data bus or associated select
lines between the host µC and
the SLIC and the SRAM.
3) 4xECLK missing to the SLIC.
4) SLIC is faulty.
5) Improper decoding logic due
to open or failure of U708 AND
logic gate.
6) SRAM is faullty.
Connections
good?
Repair
connections.
Yes
No
Signals
verfied?
During radio power up
Self-Test, verify
activity (transisitons
from high to low) on
U705 CS*.
No
Yes
Signals
verfied?
Replace U705.
MAEPF-26023-O
No Yes
No Yes
Signals
verfied?
Replace U708.Replace U701.
Replace U702.
Verify operation of
U708 and logic AND
gate. During radio power
up Self-Test, verify
activity (transisitons
from high to low) on
U708 IN_B.
During radio power up
Self-Test, verify
activity (transisitons
from high to low) on
U705 OE* and WE*.