Block check character bcc, Results in the value 13 – Metalfab SEW Eurodrive MOVIMOT MM..C User Manual
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Operating Instructions – MOVIMOT® MM03C - MM3XC
9
Function with RS-485 master
Startup with Communications Interface / Fieldbus
Block check char-
acter BCC
The block check character (BCC) is used in conjunction with even parity formation to en-
sure a reliable data transfer. The block check character is formed by means of an XOR
logic operation of all message characters. The result is transmitted at the end of the
message in the BCC.
Example
The following figure shows how a block check character is created for a PDU type 85
hex
acyclical message with three data words. The XOR logic operation on the characters
SD1 ... PO3
low
results in the value 13
hex
as the block check character. This BCC is sent
as the last character in the message. Once the receiver has received the individual char-
acters, it performs a character parity check. The block check character is subsequently
created from the characters received, SD1 PO3
low
, in accordance with the procedure
below. The telegram has been correctly transmitted if the calculated and received BCCs
are identical and there is no character parity error. Otherwise, a transmission error has
occurred. The message may have to be repeated.
01660CEN
1
TYP
ADR
SD1
PA1
hi
PA1
lo
PA2
hi
PA2
lo
PA3
hi
PA3
lo
BCC
0
0
0
0
0
1
0
0
0
0
0
0
1
0
0
1
0
1
0
0
0
1
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
1
1
1
0
1
1
0
0
0
0
1
0
0
0
1
1
0
1
1
0
P
a
rity
Stop
Star
t
SD1: 02
hex
ADR: 01
hex
TYP: 85
hex
BCC: 13
hex
XOR
XOR
XOR
XOR
XOR
XOR
XOR
XOR
Idle
02
hex
01
hex
85
hex
00
hex
06
hex
20
hex
00
hex
0B
hex
B8
hex
13
hex
Process Output Data (PO)
PA1
hi
: 00
hex
PA1
lo
: 06
hex
PA2
hi
: 20
hex
PA2
lo
: 00
hex
PA3
hi
: 0B
hex
PA3
lo
: B8
hex
0
0
I