T2: Unit Transmits Response To Host; T3: Host Acknowledges Unit Response - Advanced Energy Pinnacle User Manual

Pinnacle™ 20 kW
• If the address does not match, the Pinnacle does not respond to the host computer;
the Pinnacle 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 Pinnacle sends a negative
acknowledgment (NAK), hexadecimal 15h, to the host computer.
• If the address matches and the message is intact, the Pinnacle sends an
acknowledgment (ACK), hexadecimal 06h, to the host computer.
If the Pinnacle 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 "AE
Bus Command Status Response (CSR) Codes" on page 4-60). CSR code 0 is sent
when the command has been accepted.
If the host receives a NAK (15h) from the Pinnacle, 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 : UNIT TRANSMITS RESPONSE TO HOST
2
The Pinnacle 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 : HOST ACKNOWLEDGES UNIT RESPONSE
3
If the Pinnacle receives an ACK (15h) from the host computer, it returns to the normal
waiting state. If the Pinnacle receives a NAK (06h) from the host computer, the
Pinnacle retransmits the response packet. The Pinnacle continues to retransmit in
response to NAK transmissions until the host computer stops the cycle. If the Pinnacle
receives no response, it assumes an ACK and returns to the waiting state.
5702156-E I/O Communication and Control 4-59