[Instruction] Contents

Warning1. Although using pointer register for indirect addressing application is powerful and flexible, butchanging the V and Z values freely and carelessly may cause great damages with erroneouswriting to the normal data areas. The user should take special caution during operation.2. In the data register range that can be used for indirect addressing application (R0~R8071), the328 registers R3840~R4167 (i.e. IR, OR and SR) are important registers reserved for system orI/O usage. Writing at-will to these registers may cause system or I/O errors and may result in amajor disaster. Due to the fact that users may not easily detect or control the flexible registeraddress changes made by the V and Z values, FBs-PLC will automatically check if thedestination address is in the R3840~R4067 range. If it is, the write operation will not be executedand the M1969 flag “Illegal write of Indirect addressing” will be set as 1. In case it is necessary towrite to the registers R3840~R4067, please use the direct addressing.5.3 Numbering System5.3.1 Binary Code and Related TerminologiesBinary is the basic numbering system of digital computer. Since the PLC operates with discrete ON/OFF values, it isnatural to use binary codes. The following terminologies should be fully understood before go to further topic ofnumbering system.● Bit: (Abbreviated as B, such as B0, B1, and so on) It is the most basic unit of binary value. The status of bit is either“1” or “0”.● Nibble: (Abbreviated as NB, such as NB0, NB1, and so on)It is formed by four consecutive bits (e.g. B3~B0) andcan be used to represent a decimal number 0~9 or a hexadecimal number 0~F.● Byte: (Abbreviated as BY, such as BY0, BY1, and so on) It is formed by two consecutive nibbles (or 8 bits, such asB7~B0) and can be used to represent a 2-digit hexadecimal number 00~FF.● Word: (Abbreviated as W, such as W0, W1, and so on) It is formed by two consecutive bytes (or 16 bits, such as B15~B0) and can be used to represent a 4-digit hexadecimal number 0000~FFFF.● Double Word: (Abbreviated as DW, such as DW0, DW1, and so on) It is formed by two consecutive words (or 32 bits,such as B31~B0) and can be used to represent an 8-digit hexadecimal number 00000000~FFFFFFFF.DW←Double WordW1 W0 ←WordBY3 BY2 BY1 BY0 ←ByteNB7 NB6 NB5 NB4 NB3 NB2 NB1 NB0 ←NibbleB31 B30 B29 B28 B27 B26 B25 B24 B23 B22 B21 B20 B19 B18 B17 B16 B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 ←Bit● Floating Point Number: It is also formed by two consecutive words. The Floating Point Number can expressed themaximum range is ±(1.8*10 -38 ~3.4*10 38 ). For the details, Please refer to section 5.3.6 for explanation.5-9