Motorola ASTRO Digital Saber Service Manual page 86

Host µC
Bootstrap Failure.
Verify standard
bias per table
Table 3.
Isolate and
No Standard
repair problem.
bias OK?
See Chart C.5.
Yes
Verify voltage at VR207
(OPTB+/BOOT_SEL/VPP)
is: 10VDC≤VPP≤12.7VDC.
Isolate open
No VPP is
and repair or
correct?
adjust VPP as
required.
Yes
Verify MODA and MODB of
U204 are pulled to a logic
low state (< .8VDC).
With the host µC out of
reset and prior to any
downloading through the
Repair inverter
No
MODA and Yes (BOOT_DATA_OUT) is logic
circuit consisting
low and U204-PD0 is logic
MODB are
of VR207 and
high (BOOT_DATA_IN).
correct?
Q204.
Verify
BOOT_DATA_IN and
No
BOOT_DATA_OUT
are isolated by
MUX U208.
1
Synopsis
The host µC bootstrap mode is
used during reprogramming of
the host µC and DSP FLASH
ROMs. Refer to appropriate
Theory of operation section for
description of bootstrap
operation. Since the operating
code is downloaded through the
serial bus instead of from the
ROM and is initially executed in
the µC internal RAM, this is a
good method of verifying
operation of the µC. Basic
failure modes:
1) Necessary supplies,
grounds, system clocks not
present.
2) Vpp voltage not set to
correct voltage for bootstrap
mode select or FLASH
programming.
3) Improper configuration of
mode select pins.
4) Improper operation of RESET
to the host µC.
5) Improper
configuration/operation of the
host µC serial bus.
Note: This
configuration
indicates the
µC is in
Bootstrap
mode waiting
for data.
serial bus:
Verify U204-PD1
PD0 and PD1
are correct?
Yes
2
1
Initiate download
Verify MUX and verify the
No Yes
control on Pin
Signals are
4 of U208 is BOOT_DATA_IN is
isolated?
low. echoed out on
BOOT_DATA_OUT
Control
Yes
voltage
Replace U208.
Data echoed?
correct?
No
Repair inverter
circuit
Verify U204 ECLK
composed of
is 1.8432 MHZ
VR207 and
Q203.
No
Replace Y201. ECLK frequency
Verify download
baud rate is 7200.
No
Fix baud rate.
10-4
2
data on
.
Verify continuity
No
of BOOT_DATA_IN
from J201-15 to
U204-PD0.
Yes
No
Isolate and
Signal good?
repair open.
±200ppM.
Yes
In some
correct?
circumstances
additional code is
downloaded and
Yes
placed in external
RAM. In this
case, a failure of
the external RAM
could look like a
boostrap failure.
Baud rate Yes
Replace U204.
correct?
MAEPF-24420-A
Chart 4 . Bootstrap Fail