Ae Bus Optional Length Byte; Ae Bus Data Bytes; Ae Bus Checksum Byte - Advanced Energy Pinnacle User Manual

Pinnacle™ 20 kW

AE BUS OPTIONAL LENGTH BYTE

This field supplements the Header field and exists only when the length bits (bits 0, 1,
and 2) in the Header field contain a value of 7 (07h). If the number of data bytes in the
Data field is 6 or less, then the three length bits in the Header field are sufficient to
represent this amount 0 to 6 (00h to 06h). Since the Data field may contain up to 255
bytes of information, the Optional Length byte is required when the Data field is
larger than 6 bytes.
When the Data field is larger than 6 bytes, the length bits in the header (bits 0, 1, and
2) will equal 7 (07h) and the Optional Length byte will contain a one-byte value, from
7 to 255 (07h to ffh), representing the number of data bytes in the Data field.

AE BUS DATA BYTES

The Data field may contain from 0 to 255 bytes of binary data. This field contains
command-related data or a command status response (CSR). Since some commands
do not require data, sometimes the Data field is not present.
If the value specified in the length bits (bits 0, 1, and 2) of the Header field is 0 to 6,
the Pinnacle expects 0 to 6 data bytes. However, if the value in the Header field is 7
(07h), the Pinnacle looks for the Optional Length byte after the Command field and
reads this value to calculate the data byte count.

AE BUS CHECKSUM BYTE

This one-byte field is the last byte in the packet. The value of this byte depends upon
the number of bytes in each of the preceding fields. The transmitting unit determines
this value by accumulating the exclusive-or (XOR) 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 unit has received
the packet intact.
The unit will act on the message only if the address is valid and the checksum is
validated as having no parity errors.
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