Dressler 13150 400 V, User Manual

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HPG 13150 400 V (A) Communication Interfaces 4-27
HPG™ 13150 400 V RF Power Generator
Prerelease version
• If the address does not match, the HPG generator does not respond to the
host computer; the HPG generator resets and resumes waiting for a
message addressed to it. If the address matches but the
exclusive-or
(XOR) sum of the bytes in the packet (including the checksum) is not zero,
the HPG generator sends a negative acknowledgment (NAK),
hexadecimal 15h, to the host computer.
• If the address matches and the message is intact, the HPG generator
sends an acknowledgment (ACK), hexadecimal 06h, to the host computer.
If the HPG generator receives a request for data or status information, it
gathers and sends the requested information. Otherwise, it evaluates the
incoming command and sends a message packet that contains a one-byte
data value (CSR code) to the
Host (see “Host Port Command Status
Response (CSR) Codes” on page 4-40 ). CSR code 0 is sent when the
command has been accepted.
If the Host receives a NAK (15h) from the HPG generator, the Host either
retransmits the packet or does whatever else it has been programmed to do in
this situation. If the
Host receives an ACK (06h), it waits for the requested
data or status information, or it waits for the CSR code telling it whether or not
the new parameter was accepted. If the
Host receives no response within a
reasonable period, it takes whatever action it has been programmed to take.
T
2
: Unit Transmits Response to Host
The HPG generator prepares a response packet with the requested
information or appropriate CSR code, which it then transmits to the host
computer. The host computer then determines, by means of the checksum, if
the response packet is complete. If the host computer detects an error in the
transmission (the checksum is not validated), it can request the packet be sent
again by transmitting a NAK (15h).
T
3
: Host Acknowledges Unit Response
If the HPG generator receives an ACK (15h) from the host computer, it returns
to the normal waiting state. If the HPG generator receives a NAK (06h) from
the host computer, the HPG generator retransmits the response packet. The
HPG generator continues to retransmit in response to NAK transmissions until
the host computer stops the cycle. If the HPG generator receives no response,
it assumes an ACK and returns to the waiting state.