Technical Manual

10-8
Chart 6. 01/81 Host ROM Checksum Failure
Synopsis
This failure indicates the Host
ROM program code is incorrect.
It is implied that the host
processor found and executed
enough valid code at power up
to get to the point of verifying
the rest. Basic failure modes
are as follows:
1) The contents of U727
have been corrupted.
2) The decoding logic comprised
of U701 and U702 is not
working properly due possibly
to circuit opens or shorts or
that a failure of one or more of
these ICs has occurred.
3) U727 has failed.
Due to the fact that the Host µC
successfully initialized, a
failure in one of the ICs is not
likely.
Repair opens.
Fail 01/81
Host ROM Checksum
Failure
Connections
good?
No
Yes
Visually inspect all
leads to U727
with a 5x glass.
Check for operation of
U701 and U702 as
follows: During radio
power up Self-Test,
verify activity
(transisitons from high
to low) on U727
ROM1CS*/ROM2CS*,
and OE*.
Use ohmmeter to electrically
verify following signal
connections to source IC:
Signal @ U727 Source
HD0-HD7 U701
HA0-HA13 U701
HA14OUT,HA15OUT U702
HA16,HA17 U702
ROMCS1*,ROMCS2* U702
OE*,MEMR/W* U702
CE* U725
VCC +5V
VSS GND
Replace
U727.
No
MAEPF-26019-O
Yes
Host ROM
ReFLASH
passed?
No
Yes
Connections
good?
Repair opens.
Yes
No
ReFLASH Host
ROM
End
Initial
operation
checks
Good?
Refer to section on
Power-up Failure C.3
and/or Fails to
Bootstrap C.4.