Mitsubishi Electronics FX1S Bits, Words, BCD and Hexadecimal, Bit Devices, Individual and Grouped

FX Series Programmable Controllers Devices in Detail 4

4.14Bits, Words, BCD and Hexadecimal

FX1S FX1N FX2N FX2NC

The following section details general topics relating to good device understanding. The section is split into several smaller parts with each covering one topic or small group of topics. Some of the covered topics are;

Bit devices, individual and grouped	- see page 4-40
Word devices	- see page 4-42
Interpreting word data	- see page 4-42
Two’s compliment	- see page 4-45

Available devices:

• For PLC specific available devices please see chapter 8.

4.14.1Bit Devices, Individual and Grouped

Devices such as X, Y, M and S are bit devices. Bit devices are bi-stable, this means there are only two states, ON and OFF or 1 and 0. Bit devices can be grouped together to form bigger representations of data, for example 8 consecutive bit devices are some-times referred to as a byte. Further more, 16 consecutive bit devices are referred to as a word and 32 consecutive bit devices are a double word.

The PLC identifies groups of bit devices which should be regarded as a single entity by looking for a range marker followed by a head address. This is of the form KnP where P represents the head address of the bit devices to be used. The Kn portion of the statement identifies the range of devices enclosed. “n” can be a number from the range 0 to 8. Each “n” digit actual represents 4 bit devices, i.e K1 = 4 bit devices and K8 = 32 bit devices. Hence all groups of bit devices are divisible by 4.

The diagram and example on the following page explain this idea further........

4-37