migra MPB CAN
Large Format Graphics Compatible LED Display with CANopen Interface
Page 12
microSYST Systemelectronic GmbH, Am Gewerbepark 11, 92670 Windischeschenbach
+49 9681 91960-0,
+49 9681 91960-10, [email protected], www.microsyst.de
3.6.1 Header
STX
DA
SA
FC
LEN-H
(optional)
LEN-L
(optional)
Start of Text Destination
Address
Source
Address
Frame
Control
High Nibble
Number of
Data Bytes
Low Nibble
Number of
Data Bytes
00000010
b
(02
h
)
1XXXXXXX
b
1XXXXXXX
b
1XXXXXXX
b
1111XXXX
b
1111XXXX
b
STX:
Start of text: 02
h
DA:
Destination address:
Bit 7 must be set
⇒
possible addresses: 0 to 126
d
, or
127
d
for broadcast
SA:
Source address:
Bit 7 must be set
⇒
possible addresses: 0 to 126
d
FC:
Frame control: (control for the communications
sequence)
Bit 7:
set permanently to 1
Bits 6 - 2:
reserved (0)
Bit 1:
0 -> do not use checksum
(do not use LEN-H/L, CHK-H/L)
1 -> use checksum
(use LEN-H/L, CHK-H/L)
Bit 0:
0 -> do not send response
1 -> send response
LEN-H:
High nibble length: number of high nibble data bytes,
bits 4 through 7 must be set
(e.g. number of data bytes = 26
h
⇒
high nibble = 2
⇒
11110010
b
)
LEN-L:
Low nibble length: number of low nibble data bytes,
bits 4 through 7 must be set
(e.g. number of data bytes = 26
h
⇒
low nibble = 6
⇒
11110110
b
)
LEN-H und LEN-L only need to be transmitted if a checksum is
used. If bit 1 in the FC byte is not set, LEN-H and LEN-L may not be
transmitted!