IDEC MICRO/I HG4G-CJT22 F-B Series User Manual page 166

5 User Communication
Modbus RTU (CRC):
Conversion Type
■
After calculating the data using the specified calculation type, select the type of conversion for the data from the
following.
Hexadecimal to ASCII： Considers the data as binary-coded hexadecimal number and converts it to ASCII data.
No conversion:
Number of bytes
■
After converting according to the specifed conversion type, select 1 or 2 for the number of bytes for transmission
data.
Example: BCC for transmission command data
This example describes the case of transmitting the BCC calculation result from the following transmission data as
BCC data.
STX 1 2
(02h) (31h) (32h)
• Calculation Start Position and Calculation End Position
When Calculation Start Position is 2 and Calculation End Position is 1: Calculates the range 1234.
Calculation Start Position:
Calculation End Position:
• Calculation Type
XOR:
ADD:
ADD (2's Complement):
Modbus ASCII (LCR):
Modbus RTU (CRC):
• Conversion Type
When the BCC calculation result is 0004h, the converted data is as follows.
Data
0004h
Hexadecimal to ASCII
Data
0004h
No conversion
3-60
CRC-16 (Generating polynomial:x
procedure. Conversion Type: No conversion, Number of bytes: 2
1. Obtain an exclusive OR (XOR) of 1 byte data at Calculation Start Position and FFFFh.
2. If the least significant bit of the result of step 1 is 0, shift to the right by one bit. If the
bit is 1, shift to the right by 1 bit and obtain XOR of the result and the value (A001h).
3. Repeat step 2 to shift 8 times.
4. Obtain XOR of the next one byte of data and the result of step 3.
5. Repeat steps 2 through 4 until the data at Calculation End Position is processed.
6. Send the result of step 5 in the order of the lower byte and upper byte.
Example: 1234h→34h, 12h
No conversion is performed.
3 4 5 BCC
(33h) (34h) (35h)
(1) (2) (3)
STX 1 2
(02h) (31h) (32h)
(5) (4) (3)
Data used for BCC calculation
31h^32h^33h^34h^=04h
31h+32h+33h+34h=CAh
Inverts the bit of CAh+1=36h
100h-(12h+34h) = BAh
BA30h → BAh, 30h
0 4
(30h) (34h)
00h 04h
WindO/I-NV4 User's Manual
16 15 2
+x +x +1) is calculated according to the following
CR
(0Dh)
(4) (5) (6)
3 4 5 BCC
(33h) (34h) (35h)
(2) (1) (0)
CR
(0Dh)