101501-695 REV B
37
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5.0
COMMAND HANDLING
5.1 Command Time Out
The host computer should set a serial time out at approximately
100mS. This allows the DSP to process the incoming message and
transmit a response. The DSP will initiate a reply to incoming
messages in approximately 1-2mS, with a worst case of 5mS.
5.2 Buffer Flushing
The DSP will flush the incoming serial data buffer every time an STX is
received. This provides a mechanism to clear the receive buffer of
partial or corrupt messages.
5.3 Handshaking
The only handshaking implemented on the host interface, is built into
the implementation of this protocol. That is, the host must initiate all
communications. If the supply receives a program command, an
acknowledge message is sent back to the host via the “;” message. If
the host does not receive an acknowledge within the time out window,
the host should consider the message lost or the device off-line.
Similarly, if the supply receives a request command, the requested
data is sent back to the host. If the host does not receive the requested
data within the time out window, the host should consider the message
lost or the device off-line.
This essentially uses the full-duplex channel in a half-duplex
communication mode.
Note: During the first five seconds after the application of AC line voltage serial
data transmission from the Monoblock, if any, should be ignored. It is always
recommended that the response from the Monoblock be verified using the
checksum as outlined in paragraph 4.3.