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Command (CMD) File Generation
3-4
Generally, the CMD file header values are derived directly from the hex file and the
parameters shown above need not be included. The following situations, however,
require the use of GENCMD parameters.
• Use the 8080 keyword whenever ASM-86 is used to convert 8080 programs
that have code and data intermixed within a single 64K segment, regardless
of the use of the CSEG and DSEG directives in the source program.
• Use an absolute address (A value) for any group which must be located at an
absolute location. Normally, this value is not specified since CP/M-86
cannot generally ensure that the required memory region is available (in
which case the CMD file cannot be loaded).
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• Use the B value when GENCMD processes a hex file produced by Intel's
OH86 or a similar utility program that contains more than one group. The
output from OH86 consists of a sequence of data records with no informa-
tion to identify code, data, extra, stack, or auxiliary groups. The B value
marks the beginning address of the group named by the keyword, causing
GENCMD to load data following this address to the named group (see the
examples that follow). The B value is normally used to mark the boundary
between code and data segments when no segment information is included
in the hex file. Files produced by ASM -86 do not require the B value since
segment information is included in the hex file.
• The minimum memory value (M value) is included only when the hex
records do not define the minimum memory requirements for the named
group. Generally, the code group size is determined precisely by the data
records loaded into the area. That is, the total space required for the group is
defined by the range between the lowest and highest data byte addresses.
The data group, however, may contain un initialized storage at the end of
the group and thus no data records are present in the hex file which define
the highest referenced data item. The highest address in the data group
should be defined within the source program by including "DBO" as the last
data item. Alternatively, the M value can be included to allocate the
additional space at the end of the group. The stack, extra, and auxiliary
group sizes must be defined using the M value unless the highest addresses
within the groups are implicitly defined by data records in the hex file.
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