Texas Instruments 990 Operation Manual page 141

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5.7.1 SOURCE LISTING. The source listings show the source statements and the resulting
object code. A typical listing is shown in the example programs in Section VII.
Each page of the source listing has a title line at the top of the page if a title was supplied by a
TITL directive. A page number is printed to the right of the title area. The printer skips a line
below the title line, and prints a line for each source statement listed. The line for each source
statement contains a source statement number, a location counter value, object code assembled,
and the source statement as entered. When a source statement results in more than one word of
object code, the assembler prints the location counter value and object code on a separate line
following the source statement for each additional word of object code. The source listing lines
for a machine instruction source statement are shown in the following example:
0018 0156 C820
0158 0128'
015A 0003
MOV @INIT+3,@3
The source statement number, 0018 in the example,
is
a four-digit decimal number. Source
records are numbered in the order in which they are entered, whether they are listed or not. The
TITL, LIST, UNL, and PAGE directives are not listed, and source records between a UNL
directive and a LIST directive are not listed. The difference between source record numbers
printed indicates how many source records are not listed.
The next field on a line of the listing contains the location counter value, a hexadecimal value.
In the example, 0156 is the location counter value. Not all directives affect the location counter,
and those that do not affect the location counter leave this field blank. Specifically, of the
directives that the assembler lists, the IDT, REF, DEF, DXOP, EQU, and END directives leave
the location counter field blank.
The third field contains the hexadecimal representation of the object code placed in the location
by the Assembler, C820 in the example. The apostrophe following the third field of the second
line in the example indicates that the contents, OI2B, is relocatable. All machine instructions and
the BYTE, DATA, and TEXT directives use this field for object code. The EQU directiye places
the value corresponding to the label in the object code field.
In listings printed by PX9ASM, the third field may contain two or four hyphens (-) instead of
hexadecimal digits. This occurs when a forward reference determines the values of these digits.
Later, when the forward reference is defined, the assembler prints an additional line in the listing
following the statement that defines the forward reference. This line contains the location being
resolved, two asterisks
(**),
and the contents. An error-free listing will include such a line for
each location previously printed with hyphens as the contents. The listings printed by the other
assemblers do not contain this type of information because all references are either resolved or
identified as undefined before the listings are printed.
The fourth field contains the first 60 characters of source statement as supplied to the assembler.
Spacing in this field is determined by the spacing in the source statement. The four fields of
source statements will be aligned in the listing only when they are aligned in the same character
positions in the source statements or when tab characters are used .
.
The machine instruction used in the example specifies the symbolic memory addressing mode for
both operands. This causes the instruction to occupy three words of memory and three lines of
the listing. The object code corresponds to the operands in the order in which they appear in the
source statement.
5-5
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