Timers perform timing for operations. The timer contains a coil, contact, and a time
value register. When the coil is electrified, and the setting value for the timer is reached,
the contact is actuated (contact A closes, contact B opens), and the timer's fixed value is
given by the setting value. A timer has a regulated clock cycle (timing units: 100 ms). As
soon as power to the coil is cut off, the contact is no longer be actuated (contact A
opens, contact B closes), and the original timing value returns to zero.
Timer devices are indicated by: T0, T1–T159, and so on. These devices are
indicated by the symbol T, and the device’s order is indicated with a decimal
number.
Data registers are used exclusively to store data and various parameters. When you
use a PLC is to perform various types of sequence control, set time values, and count
value controls, the PLC performs data processing and numerical operations and stores
the operands, parameters, and results in data registers. Each data register contains 16
bits of binary data (one word). Two data registers with adjacent numbers can process
double words.
Data register devices are indicated by: D0, D1– D399, and so on. These devices
are indicated by the symbol D, and the device’s order is indicated with a decimal
number.
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