CHAPTER 13 RS-485 COMMUNICATIONS

No.

Calculations

15 14 13 12 11 10 9

bit

87

6

5

4

3

2

1

0 Shift carry

41 DT[5] (No. of registers (L)) 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0

42 CRC = No.40 XOR No.41 0 1 0 1 0 0 0 0 0 0 0 0 1 0 0 0

43 Shift CRC by 4 bits to the right 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0

1

44 CRC = No.43 XOR No.2 1 0 1 0 0 1 0 1 0 0 0 0 0 0 0 1

45 Shift CRC by 1 bit to the right 0 1 0 1 0 0 1 0 1 0 0 0 0 0 0 0

1

46 CRC = No.45 XOR No.2 1 1 1 1 0 0 1 0 1 0 0 0 0 0 0 1

47 Shift CRC by 1 bit to the right 0 1 1 1 1 0 0 1 0 1 0 0 0 0 0 0

1

48 CRC = No.47 XOR No.2 1 1 0 1 1 0 0 1 0 1 0 0 0 0 0 1

49 Shift CRC by 1 bit to the right 0 1 1 0 1 1 0 0 1 0 1 0 0 0 0 0

1

50 CRC = No.49 XOR No.2 1 1 0 0 1 1 0 0 1 0 1 0 0 0 0 1

51 Shift CRC by 1 bit to the right 0 1 1 0 0 1 1 0 0 1 0 1 0 0 0 0

1

52 CRC = No.51 XOR No.2 1 1 0 0 0 1 1 0 0 1 0 1 0 0 0 1

13

13-30 Modbus RTU Communications