Texas Instruments 990 Operation Manual page 55

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The object code of a module may also contain a symbol similar to an external reference, but
different in two respects. The symbol is the first six characters of the IDT character string of
one of the program modules to be linked, and a zero value
is
associated with the symbol. The
symbol is used by PX9LAL to identify a required module. The zero inhibits any attempt to
perform linking. When more than one program module is to be loaded, the first module must
contain at least one reference of this type and may contain one for each module of the load.
Printed Output. The printed output of PX9LAL is a full or partial load map. This map shows
the name and load point of each module that is loaded. The full map also includes the symbols
and the corresponding memory addresses of any external definitions in the module. Both types
of maps contain only names of modules that have been loaded because they were referenced.
3.4.6.2 Operational Messages. When PX9LAL is started by the LL command, a series of
messages requesting user responses are given. The messages are the following.
LD PT?
Load Point. The user should input the hexadecimal memory location of the load point
for the object module. If a carriage return is entered, the default value of 0 will be
assumed.
LD BI?
Load Bias. The user should input the hexadecimal value of the load bias for the object
module or modules to be loaded. If a carriage return is entered, the default value
OOA0
16
will be assumed.
The load point and load bias specified above are used in determining how the code is
relocated and the memory address where the code will actually be loaded. Code
assembled with an absolute origin (AORG) directive will be loaded at the absolute
address determined by the directive plus the load point.
MEMLOC
=
ABS ADDR
+
LD PT
Code assembled with a relocatable origin (RORG) directive will be loaded at the
relocatable address determined by the directive plus the load bias plus the load point.
MEMLOC
=
REL ADDR + LD BI + LD PT
Note that the relocation is performed on the code using the load bias only. Specifying
a load bias is equivalent to placing a D tag with that bias before the module being
loaded. The load point is only used to determine the actual memory location where
the code will be loaded.
Object code loaded with a load point not equal to the default 0 is not executable. This
feature has been included in the linking loader for special Prototyping System
applications.
3-17
Digital Systems Division