Measurement Specialties 9116 - Manual (Page 61)

Pressure Systems, Inc. Model 9116 User’s Manual
Page 52 www.PressureSystems.com
Command ‘c’— Sub-command Index 01: Start Stream(s)
This sub-command is used to start the delivery of any previously configured host stream in a
module. If the stream started is of “continuous” duration, then it will be necessary to use the
Stop Stream sub-command later. Otherwise, the stream will end automatically if a finite number
of packets has been specified for it. This sub-command may also be used to resume a
previously stopped host stream that has not transmitted all requested data packets. The sub-
command’s format is:
Command
“c 01 st”
‘c’ is the command letter
‘01’ is the sub-command index (‘ii’) for Start Stream(s)
‘st’ is the stream id digit (1, 2, or 3, or 0=all streams)
NOTE: all parameters are separated by a space character.
Response
“A”
‘A’ is the acknowledge letter
Autonomous
Packet “tssss[dddd] .. [dddd]”
‘t’ is a 1-byte binary (8-bit) value identifying the stream number (1-3).
‘ssss’ is a 4-byte binary integer (32-bit, big-endian) packet sequence.
number. Optional binary status may follow the sequence number. (See
“05” sub-command.)
‘dddd’ are the acquired datum values in the selected format plus a leading
space (except f=7 or 8).
Description: This sub-command starts a particular specified host stream (st=1-3), or starts all
configured host streams with a single command (st=0). Each autonomous host
stream packet begins with a 5-byte fixed-format (binary) data header (tssss).
The first byte (t) identifies the host stream, while a 32-bit unsigned binary
sequence number (ssss) completes the header. This sequence number will start
at one (1) for the first packet returned by a stream and increment for each other
returned packet of that stream. In the case of a “continuous” data stream, the
sequence number may overflow the maximum permissible 32-bit integer value. If
this occurs, the sequence number value will wrap around to zero (0) following the
largest 32-bit value (4294967295) and then continue to increment by one for
each returned packet. The sequence number field is intended to provide a
mechanism for host software to ensure that host data stream packets are
processed or stored in the order in which they were obtained by the module.
Each of the three possible host streams will report their own unique sequence
number. Note that if a previously stopped data stream is restarted, the returned
sequence numbers will resume with the next number at the point of the stream’s
termination. The sequence numbers will not restart at one (1) if a scan list is
temporarily stopped and then restarted without reconfiguring the stream. A
“limited” stream will terminate once this sequence number equals the requested
number of packets for the stream. If a “limited” stream is restarted after expiring,
it will restart at sequence number 1.