This chapter is about PLC operations involving blocks of data representing a value, such blocks being termed words and stored in registers. Data handling involves such operations as moving numeric information from one location to another, comparing data values and carrying our simple arithmetic operations. Programs involving such operations are developed.
Timers, counters, and individual internal relays are all concerned with the handling of individual bits, that is, single on/off signals. Shift registers involve a number of bits with a group of internal relays being linked (see Chapter 11). The block of data in the register is manipulated. This chapter is about PLC operations ...