Chapter 9 PLC Counter Instructions 195 9.6 Cascading Counters In some industrial applications, counters are cascaded so that one counter increments or decrements when another counter is done. This type of application is used mainly in material handling and process control environments. For example, cascading counter instructions can be used in the part packaging industry. Six bottles of water are packaged together and placed in a new container. One counter could be used to count to six. A second cascaded timer would then be used to count the number of containers. Example 9-4 illustrates how to create a PLC ladder logic diagram in which two count-up instructions are cascaded together. Examine Figure 9-8. This fi gure displays the PLC ladder logic diagram for Example 9-4. fi 0000 0001 0004 0005 CTU Count up Counter C5:0 Preset 10 Accum 0 End CU DN CU DN CTU Count up Counter C5:1 Preset 5 Accum 0 Pushbutton 0 I:0 DN C5:0 0002 0003 RES Switch 1 I:0 C5:0 DN C5:1 Green_PLT 0 O:0 DN C5:0 RES Switch 1 I:0 C5:1 Goodheart-Willcox Publisher Figure 9-8. PLC ladder logic diagram for Example 9-4. Example 9-4