Computer Hardware User Manual

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 different 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