Hitachi SJ7002 Series Instruction Manual page 303

Block Check
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
Code (BCC)
transmission. The example below shows command 01 setting the inverter frequency to 5Hz.
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.
ASCII Code Table
The table below shows only the ASCII codes used for function codes and parameter data.
Frame format
STX Node Command Data
Data bytes:
3 0 3 1 3 0 3 1
0 1
3 1
0 0
3 0
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
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
SJ700 Inverter
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
b 6 2
— —
B–19