Block Check Code (Bcc); Ascii Code Table - Hitachi SJ300 Series Instruction Manual

B–18
Communications Reference Information
Block Check
Code (BCC)

ASCII Code Table

This section shows how the inverter protocol computes defines a BCC—block check code. The
BCC is calculated for each frame transmitted and can be used to verify the integrity of data
transmission. The example below shows command 01 setting the inverter frequency to 5Hz.
Frame format
STX Node Command
The block check code is computed by using the ASCII codes (shown above) and applying
eXclusive OR (XOR) operations. Beginning with the first pair of bytes, the result of their XOR
result is then used in an XOR operation with the third byte, and so on. For this example, the
BCC calculation is shown below.
Data bytes:
3 0 3 1 3 0 3 1
0 1
3 1
0 0
3 0
The table below shows only the ASCII codes used for function codes and parameter data.
Character ASCII Code
STX 0 2
ACK 0 6
CR 0 D
NAK 1 5
0 3 0
1 3 1
2 3 2
3 3 3
Data BCC [CR]
0 1
0 1
0 0 0 5 0 0
0
3 0 3 0 3 0 3 5
0 0
3 0
0 5
3 5
Character ASCII Code
4 3 4
5 3 5
6 3 6
7 3 7
8 38
9 39
A 4 1
B 4 2
ASCII Code
(0x 02)
(0x 30 31)
(0x 30 31)
(0x 30 30 30 35 30 30)
(0x 30 35)
(0x 0D)
3 0 3 0
XOR
intermediate results
0 5 BCC
Character ASCII Code
C 4 3
D 4 4
E 4 5
F 4 6
H 4 8
P 5 0
— —
— —