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Equate Code (Equ); Base Register Controlling Codes (Using, Drop); Extended Mnemonic Instructions - RCA Spectra 70 Training Manual

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Example
of
CSECT
NAME
OPERATION
OPERAND
BGN
START
1000
If
no ORG
SEG2
entry, then a
segment will
CSECT
be loaded
ORG
BGN+100
following the
previous segment
CSECT
ORG
SEG2
END
The above example illustrates a program consisting
of three segments. The second segment is loaded at
HSM location 11 00 1 O. The third segment will over lay
the first two segments at the location named SEG2.
EQUATE CODE
The Equate (EQU) command assigns symbolic names
to values, or assigns the same address to two sym-
bolics. The statement,
NAME
OPERATION
OPERAND
XYZ
EQU
6
enters the name XYZ in the symbol table, and to it,
assigns the value 6. One name may be equated to
another in similar fashion.
NAME
OPERATION
OPERAND
BTAG
EQU
ATAG
The above statement causes the Assembly to enter
the name BT AG in the table, and assign to it the
address previously assigned to ATAG. The symbol
appearing in the Operand field must have been pre-
viously defined. It must have appeared in the name
field of a prior statement.
BASE REGISTER CONTROLLING CODES
The USING Code indicates to the Assembler what
base address values will be in specific general re-
gisters at object time.
The Assembler creates a
table of these values, and then uses them to assign
21
registers and to compute displacements when base
references are not included in an expression. (See
page 3).
The first operand denotes the value assumed to be in
a register.
The second operand specifies the regis-
ter.
NAME
OPERATION
OPERAND
USING
USING
STARTP+6,5
*-10,6
The first operand may be a relocatable expression
while the second is simple and absolute.
The USING code does not load a general register. A
Load Multiple, Move Character or Branch and Link
instruction places the actual base address in a gen-
eral register.
The assumed value of a register may be altered by
incorporating another USING statement at any place
in the source program.
NAME
OPERATION
OPERAND
USING
*+500,5
The only function of the DROP code is to delete a
base value from the Assembly table.
NAME
OPERATION
OPERAND
DROP
6
It is not necessary to drop a base address from the
table prior to changing it with a second USING state-
ment.
EXTENDED MNEMONIC INSTRUCTIONS
The assembler provides a Simplified method of de-
fining the various options available via the Branch on
Condition instruction. The pseudo operation codes
listed below replace the BC and the associated mask.

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Spectra 70/25