67
Program
Memory addresses start at 00000
and run until the capacity of Program
Memory has been exhausted. The first word at each address defines the instruc
-
tion. Any definers used by the instruction are also contained in the first word.
Also,
if an instruction requires only a single bit operand (with no definer), the bit
operand
is also programmed on the same line as the instruction. The rest of the
words
required by an instruction contain the operands that specify
what data is
to
be used. When converting to mnemonic code, all but ladder diagram instruc
-
tions
are written in the
same form, one word to a line, just as they appear in the
ladder diagram symbols. An example of mnemonic code is shown below. The
instructions used in it are described later in the manual.
Address Instruction Operands
00000 LD HR 0001
00001 AND 00001
00002 OR 00002
00003 LD NOT 00100
00004 AND 00101
00005 AND LD 00102
00006 MOV(21)
000
DM 0000
00007 CMP(20)
DM 0000
HR 00
00008 LD 25505
00009 OUT 00501
00010 MOV(21)
DM 0000
DM 0500
00011 DIFU(13) 00502
00012 AND 00005
00013 OUT 00503
The
address and
instruction columns of the mnemonic code table are filled in for
the
instruction word only
. For all other lines, the left two columns are left blank. If
the instruction requires no definer or bit operand, the operand column is left
blank for first line. It is a good idea to cross through any blank data column
spaces
(for all instruction
words that do not require data) so that the data column
can be quickly scanned to see if any addresses have been left out.
When
programming, addresses are automatically displayed and do not have to
be
input unless for some reason a dif
ferent location
is desired for the instruction.
When converting to mnemonic code,
it is best to start at Program Memory ad
-
dress 00000 unless there is a specific reason for starting elsewhere.
4-4-3 Ladder Instructions
The
ladder instructions are those instructions that correspond to the conditions
on
the ladder diagram. Ladder instructions, either independently or in combina
-
tion with the logic block instructions described next, form the execution condi-
tions upon which the execution of all other instructions are based.
Basic Ladder Diagrams Section 4-4
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