Next Advance SP2200 - Manual (Page 33)

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SP2200Programmable Syringe
Pump
Publication #1200-02 28 04/29/10
8.3.3 RS-232 Protocol: Safe Mode
Command syntax (to pump):
<safe command protocol> => <STX> <length> <command data> <CRC 16> <ETX>
Response syntax (from pump):
<safe response protocol> => <STX> <length> <response data> <CRC 16> <ETX>
Safe mode uses a more structured protocol, including detection of corrupted communications, communications
time outs, and auto-alarm responses. Safe mode is enabled using the ‘SAF’ command whose parameter setting
is stored in the non-volatile memory.
Safe mode uses a modified master-slave protocol, whereby the pump transmits in response to a received
command. But, the pump also automatically transmits a status packet when an alarm condition occurs.
Corrupted communications is detected using the 16 bit CCITT CRC algorithm computed over <transmitted
data>. Packets transmitted and received include the CRC within the packets.
The parameter sent with the “SAF” command is the communications time out. This time out, in seconds, is the
time between the reception by the pump of consecutive valid communications packets. Each time a valid
communications packet is received, the time out is reset. If the time out elapses, a pump alarm will occur,
stopping the pump and the Pumping Program. The buzzer will sound, if alarms are enabled, alerting the user.
The communications time out timer will not restart until the next reception of a valid packet.
In addition, there is a 0.5 second packet inter-byte time out. While receiving a communications packet, and
before its complete reception, if a delay of 0.5 seconds occurs between bytes, the incomplete packet will be
discarded.
With the Auto-Alarm feature, whenever a pump alarm occurs, such as a pump stall, a response packet with the
alarm status information will automatically be transmitted.
Until the Safe Mode is disabled, each time power is applied to the pump, the pump defaults to the Safe mode of
communications, but the communications time out timer will not be enabled until the first reception of a valid
packet.
Although the communications time out timer is not enabled, the Auto-Alarm feature will be enabled.
Therefore, the pump will be in an Auto-Alarm only communications mode.
When power is applied to the pump, or if the system should reset, a system reset alarm occurs. The Auto-
Alarm feature, therefore, alerts the host computer that a pump reset has occurred.