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CHAPTER 21
21.
PATCH COMMAND
The
PATCH
command
allows
changes
to
be
made
to
memory-image Files.
An ob Ject File can
be
UFixed"
due
to
minor
bugs 'or
assembl~
errors without having to re=edit and
re-assemble its
corr~sponding
source File.
The
"Fixes"
can
be
entered
using
M6800
assembly language mnemonics or the
equivalent hexadecimal operation codes.
21. 1 Use
The
PATCH command
15
invoked with the
rollo~ing
command
1 ine:
where
Ti Ie.
number
<name:>.
if
the
PATCH <name:>
<name>
is
the
file specification of a
memory-image
The default suffix "LO" and the default
logical
unit
zero will be supplied if none are explicitly given ror
One
0'
the
stan~ard
error
messages will be
displayed
file
<name> does not exist or
~f
it is aT the wrong
f i
1
e format.
The
PATCH
command is an interactive program that has its
own
command
structure.
Once
PATCH
is
running,
it
will
display a
greater-than
sign
(»
as
an
input
prompt
to
indicate
that
a
command
must
be entered by the operator.
Commands exist to assign an oFfset used as a base address Tor
acceSSing
the
file,
to calculate the relative addresses for
branches,
to dis-assemble opcodesl
to
search
the
file
for
eight-
or
sixteen-bit
patterns,
to
display
and
change
locations in the fileJ
and to change the
starting
execution
address of the file.
If
the
file <name> exists and is of the proper format,
the
PATCH
command will display the
following~
nnnn cc
>
The ;; n n n n :: i s the a b
$
0
1 ute hex ad
e
c i ma 1
add
reS S
0
r
the
lowes
t
location
or
the memory-image
~ile
and is used as the initial
offset (section
21. 2. 2>'
The "cc" is the hexadecimal content
Or
that location.
The second line is the PATCH input prompt.
The following sections describe
the
various
commands
that
comprise the
PATCH
command
s~t.
Page
21-01
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