B&B Electronics RS-232 to J1939 Converter CE 1939STB User Manual
Page 32
30 1939STB4600
Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445
Function
This is used to show where the message came from. Refer to Table 37. If
the Nibble 2 is set to 0, then the message is from the J1939 bus. If Nibble 2 is
set to 2, it is an internal message (for example, Vendor ID).
MC
This is a byte from the controller. Nibble 2 is the number of data bytes (0-
8) in the message. Nibble 1, Bit 3 is the message direction. Bit 2 should
always be set to 1. Bit 1 and 0 are not used.
Table 38. MC
Nibble 2
Nibble 1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0