Command (CMD) File Generation
• The maximum memory size (X value)
is
generally used when additional free
memory may be needed for such purposes as
1/0
buffers
or
symbol tables.
If
the
data
area size
is
fixed, the X
parameter
need
not
be included.
In
this
case, the X value
is
assumed
to
be the same as the M value. The value
XFFFF
allocates the largest memory region available but
if
it
is
used, the
transient
program
must know
that
a three-byte length field
is
produced
in
the base page for this
group
where the high
order
byte may be non-zero.
Programs converted directly from
CP/M-SO,
or
programs
that
use a two-
byte pointer
to
address buffers, should restrict this value
to
XFFF
or
less,
producing a maximum allocation length
of
OFFFOH bytes.
For
example, the following
GENCMD
command
line transforms the file X.HS6
into the file
X.CMD
with the proper header record.
gencmd x code[a40] data[m30,xfff]
In
this case, the code group
is
forced
to
paragraph
address 40H or, equivalently,
byte address
400H. The
data
group
requires a minimum
of300H
bytes,
but
can use
up
to
OFFFOH bytes, if available.
As
another
example, assume a file Y .H86 exists on Drive B
and
consists
of
Intel hex
records with no interspersed segment information. The command
gencmd b:y data[b30,m20] extra[b50] stack[m40] xl[m40]
produces the file
Y.CMD
on
Drive B by selecting records beginning
at
address
OOOOH
for the code segment,
and
records beginning
at
address 300H for the
data
segment. The extra segment
is
filled from records beginning
at
500H, while the stack
and
auxiliary segment
#1
are uninitialized areas requiring a minimum
of
400H bytes
each.
In
this example, the
data
area
requires a minimum
of200H
bytes. Note again
that
the B value need
not
be included
if
the Digital Research ASM-86 assembler
is
used.
3-5
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