Apex Digital 5708009-C - Manual (Page 86)

4-40 5708009-C
Advanced Energy
®
The host computer must finish one transaction with the Apex generator before it
initiates another one, either with the same unit or any other unit.
Note: The Apex generator sends data through pin 2 (TXD.D). This pin must be
connected to the receive pin (RXD.D) on the host computer’s PC serial
connector. The receive pin is normally pin 2 for a standard, 9-pin PC serial port
and normally pin 3 for a standard, 25-pin PC serial port.
AE BUS PROTOCOL
The AE Bus protocol uses pure binary data (nothing is coded in ASCII) and is
designed to facilitate direct communications between a host computer and the Apex
generator.
The AE Bus message packet combines chunks of information in such a way that
groups of information can be sent over communications lines at one time. Five types
of information (fields) make up communications message packets (see Figure 4-5.):
• Header (address and the length of Data field)
• Command (see the AE Bus command list later in this chapter)
• Optional length byte
• Data
• Checksum (aids in error checking)
Figure 4-5. shows the organization of these data fields in the AE Bus message packet.
The subsequent paragraphs describe each data field in detail.
Figure 4-5. Graphic representation of a RS-232, AE Bus message packet
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 1 0 7 6 5 4 3
Data (0-255 bytes) Command
0-FFh
Header
5-bit address
3-bit length
Optional Checksum
1138