Programmable Logic Controllers, 5th Edition

Chapter 11. Shift Registers

The term register is used for an electronic device in which data can be stored. An internal relay (see Chapter 7) is such a device. The shift register is a number of internal relays grouped together that allow stored bits to be shifted from one relay to another. This chapter is about shift registers and how they can be used when a sequence of operations is required or to keep track of particular items in a production system.

11.1. Shift Registers

A register is a number of internal relays grouped together, normally 8, 16, or 32. Each internal relay is either effectively open or closed, these states being designated 0 and 1. The term bit is used for each such binary digit. Therefore, if we have eight internal relays in ...