Introduction to common PLC transmission instructions

Single data transfer instruction

The single data transfer instruction is used to transfer a data. According to the different word lengths of the transferred data, it can be divided into byte, word, double word and real number transfer instructions. The function of the single data transfer instruction is to send the data in the unit specified by the IN terminal to the unit specified by the OUT terminal when there is input at the EN terminal (ie EN=1).

The description of single data transfer instruction is shown in Table 6-3.

Table 6-3 Single data transfer instruction description

The operands and their data types allowed for byte, word, double word and real number transfer instructions are shown in Table 6-4.

Table 6-4 Operands and data types allowed for byte, word, double word and real number transfer instructions

Byte transfer instruction

The function of the byte immediate transfer instruction is to immediately transfer a byte of data between the physical I/O terminal and the memory when there is an input at the EN terminal (enable terminal). The byte immediate transfer instruction can be divided into the byte immediate read instruction and the byte immediate write instruction, which cannot access the expansion module. The PLC uses a cyclic scanning method to execute the program. If an instruction in the program has just been executed, it will take a scan cycle to execute again. However, the immediate transfer instruction can be executed immediately without waiting when the input is ON.

Table 6-5 shows the description of byte immediate transfer instructions.
Table 6-5 Description of byte immediate transfer instructions

The operands allowed by the byte immediate read/write instructions are shown in Table 6-6.
Table 6-6 The operands allowed by the byte immediate read/write instructions

Data block transfer instructions

The function of the data block transfer instruction is to send the data in the N units of the first address specified by the IN terminal to the N units of the first address specified by the OUT terminal when there is an input at the EN terminal (enable terminal). The data block transfer instruction can be divided into byte block, word block and double word block transfer instructions. The description of the data block transfer instruction is shown in Table 6-7.

Table 6-7 Data block transfer instruction description

The operands allowed for byte, word, and double word block transfer instructions are shown in Table 6-8.

Table 6-8 Operands allowed for byte, word, and double word block transfer instructions

Byte swap instructions

The function of the byte swap instruction is to swap the high byte and low byte of the data in the specified unit at the IN terminal when there is input at the EN terminal.

The byte swap instruction description is shown in Table 6-9.

Table 6-9 Byte swap instruction description