Control Byte 4
When control byte 3 is set to “external commands” (bit 4 set to 1), nibble 1 of control byte 4 is used to tell the J1939 in which message slot location (1 through 15) to place the message data. NOTE: Message location number 15 is receive only.
Table 7. Byte 4
|
| Nibble 2 |
|
| Nibble 1 |
|
| ||
Bit 7 | Bit 6 |
| Bit 5 | Bit 4 | Bit 3 | Bit 2 |
| Bit 1 | Bit 0 |
When control byte 3 is set to “ internal commands” (bit 5 set to 1), nibble
1 of control byte 4 has the following functions:
| Table 8. Nibble 1 Bit Values | |
Nibble 1 Value |
| Function |
0001 |
| Display vender number & version |
0010 |
| Set baud rate, stop, start bits |
0100 |
| Not used |
1000 |
| Not used |
Nibble 2 of control byte 4 is reserved for future use and is set to 0.
1939STB4600 Manual | 7 |
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