Periodic Message Commands; Vpw Mode; Jumper Jp3; Communications - AVT 84 Series Manual

message every 2.4575 seconds.
74 0C 06 01 02

9.4.5 Periodic Message Commands

All commands are listed in the Commands and Responses section at the end of this document.
A brief summary of them is provided here.
• 5x 63
• 7x 0C
• 7x 18
• 7x 1A
• 7x 1B
• 7x 1C

10. VPW Mode

Enter VPW mode with the $E1 33 command.
The report $91 07 indicates the AVT-84x has entered VPW operations.
The AVT-84x supports J1850 VPW operations in both 1X and 4X speed modes. It also supports GM
block transfers of up to 4112 bytes.
When VPW mode is first entered, the following defaults are set:
• VPW operations are enabled.
• 1X mode is enabled.
• Receive network messages are enabled.
• Match bytes are disabled.
• Transmit acks are enabled and consist of the bytes "01 60."

10.1 Jumper JP3

Jumper JP3 on the AVT-84x board connects / disconnects the VPW network from pin #2 of P3; the
DA-15P "Vehicle" connector. Usually, the factory default position of JP3 is installed.
AVT-841 revision "A" boards do not have jumper JP3. The VPW network is always connected to pin
#2 of P3; the DA-15P "Vehicle" connector.

10.2 Communications

J1850 VPW messages consist of a maximum of 11 bytes.
The AVT-84x handles the CRC byte. The host computer should never send it and the AVT-84x will
never report it.
J1850 VPW communications on GM vehicles generally follow this format:
byte #1:
byte #2:
byte #3:
AVT-84x Multiple Interface
Timer interval
Periodic message group operation control (disabled, Type1, Type2)
Define a periodic message
Periodic message disable/enable
Periodic message interval
Disable all periodic messages
Disable all groups
Priority / Type byte.
Destination address (can be function or physical).
Source address (always physical).
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