Creating An Ideal Communications Transaction; Figure 4-17. Ae Bus Communications Transaction - Advanced Energy Pinnacle 20 kW Manual

Advanced Energy

Creating an Ideal Communications Transaction

Figure 4-17 is a simplified graphic showing the steps in an ideal communications transaction
between a host computer and a Pinnacle unit.
Host

Figure 4-17. AE Bus communications transaction

First, the host computer sends a message packet to the Pinnacle unit. The packet contains one
of the following:
• A command that requests data or status information
• A command and data that change a parameter setting
• An executable command
Once the Pinnacle unit receives the message packet, the Pinnacle unit verifies that the message
is intended for it and not for another unit in the network. At this time, the Pinnacle unit also
analyzes the checksum to verify that the message was received correctly.
If the address does not match, the Pinnacle unit does not respond to the host; the Pinnacle unit
resets and resumes waiting for a message addressed to it. If the address matches but the XOR
(exclusive-or) sum of the bytes in the packet (including the checksum) is not zero, the Pinnacle
unit sends a NAK (negative acknowledgment, hex code 15h) to the host. If the address
matches correct and the message is intact, the Pinnacle unit sends an ACK (acknowledgment,
hex code 06h) to the host.
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