Okuma Alarm-B 2220 Subscript left side illegal
Illegal command in the left part of the expression
Schedule program -> In the VSET sequence, a command specified on the left side is not either common variable (V1 to V32) or output variable.
Main program, sub program -> A command specified on the left side is not any of G, M, address character, extended address character, local variable, common variable, system variable, or output variable.
Address character: NC-defined variable expressed in an alphabetic character except G, M, N, O, and V
Extended address character: NC-defined variable expressed in two alphabetic characters
Local variable: variable named and used by the user
<2 alphabetic characters><2 alphanumeric characters>
Common variable:variable commonly used in main and sub programs
System variable:system-defined variable that the user cannot rename
Output variable:variable effective in signal output to external equipment
SYSTEM (None with schedule program)
XXYY:Classification code of factor and parameter designated at left part
XX:Factor classification code
Probable Faulty Locations
Command designated in the left part
VDIN  = 5Input variables and numerical values control be designated in the left part
20 = VTOFX 
Measures to Take
Do not designate a command for which the use is not allowed.