Checksum; Creating An Ideal Ae Bus Communications Transaction; Figure 4-17. Ae Bus Communications Transaction - Advanced Energy Pinnacle Plus+ User Manual

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CHECKSUM

This one-byte field is the last one in the packet. The content depends on the value of
each of the preceding fields. The transmitting unit determines this value by
accumulating the XOR (exclusive-or) of all bytes of the packet up to, but not
including, the checksum value. The receiving unit accumulates the XOR of all bytes
of the packet, including the checksum. If the result is zero, the packet has likely been
received intact.
Only after the checksum of a message packet is validated (having no parity errors, and
the address is valid) will the Pinnacle Plus+ unit act on the message (which consists of
the contents of the command, and if appropriate, the data fields).

Creating an Ideal AE Bus Communications Transaction

The figure below is a simplified graphic showing the steps in an ideal communications
transaction between a host computer and a Pinnacle Plus+ unit.

Figure 4-17. AE Bus communications transaction

First, the host computer sends a message packet to the Pinnacle Plus+ unit. The packet
contains one of the following:
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