Ae Bus Header Byte; Ae Bus Command Number Byte; Ae Bus Optional Length Byte; Ae Bus Data Bytes - Advanced Energy HFV 8000 User Manual

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AE BUS HEADER BYTE

The first byte in each packet contains two pieces of information: five bits contain the
packet address, and three bits contain the data byte count. If the message packet
originates with the host computer (master), the address specifies the packet destination
(to an HFV generator, for example). If the packet is going to the host, the address
specifies the packet origin (from the HFV generator). The address section of the
Header field is five bits long (bits 3-7), which allows a total of 32 distinct addresses.
Address 0 (zero) is reserved for the network broadcast address; when this address is
used in a host-originated packet, all units execute the packet (but do not respond to the
host).
The remaining three bits (bits 0, 1, and 2) are the length bits. These bits tell the
receiving unit how long the Data field is so that the unit can determine when it has
received the entire message. If the Data field contains more than 6 bytes, the value of
these three bits will be set to 7 (07h), and the Optional length byte field will contain a
value indicating the number of data bytes in the Data field.
Note: The value of these bits refers only to the number of actual data bytes in the Data
field. Do not include the checksum byte when calculating the value for these
bits (see

AE BUS COMMAND NUMBER BYTE

This one-byte field contains an 8-bit value from 0 to 255 (00h to ffh) representing the
command number. If the message packet originates with the host computer, this value
specifies the purpose of the message packet. If the message originates with the HFV
generator, the value specifies the command to which it is responding. See
Commands" on page 4-17

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.
4-14
"AE Bus Checksum Byte" on page
for a complete list of commands.
Communication Interfaces
4-15).
"AE Bus
5705211-C