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1939STB4600 Manual 17
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
Byte 6
Table 25. Byte 6
Byte 6
Bit Function Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
RMTPND TXRQ MSGLIST/CPUUPD NEWDAT
Remote Pending 1 0
0 1
Transmit Request 1 0
0 1
Message lost/ CPU update 1 0
0 1
New data in message slot 1 0
0 1
NOTE: the dark gray (white letters) should be set to this value when sending a new message to
the 1939STB.
RMTPND Bits 7 and 6
Remote Pending (used for messages that are to be transmitted). Indicates
that the transmission of this object has been requested by a remote node, but
the data has not been sent yet. When RMTPND is set the controller also sets
TXRQ. Both RMTPND and TXRQ are cleared when the message has been
sent successfully.
TXRQ Bits 5 and 4
Transmit Request. This message is in the process of being transmitted and is
not finished yet.
MSGLST/CPUUPD Bits 3 and 2
This pair of bits has a dual function based on its direction.
Receive
MSGLST. Message Lost indicates the J1939 controller has stored a new
message into this location while NEWDAT was set. The previous message
was overwritten. This can occur for several reasons. The MPU was busy
doing other tasks, transmitting a serial message, error checking or servicing a
message with a higher slot number.
Transmit
CPUUPD. CPU update inhibits the transmission of a message while the CPU
updates the information. It can also be used to control the automatic
transmission of a message.