Pressure Systems 98RK-1 Command c- Sub-command Index 01 Start Stream, “c 01 st”, Response, Packet

Pressure Systems, Inc. 98RK-1 & 9816 User’s Manual©

Command 'c'— Sub-command Index 01: Start Stream

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.
	‘ st’ is the stream id digit (1, 2, or 3, or 0=all streams).
	NOTE: all parameters are separated by a space.
Response	“A”
	‘A’ is the acknowledge letter
Autonomous	“tssss[ dddd[ dddd]...”
Packet
	‘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.
	‘ dddd’ are the selected acquired datum values in the selected format, plus
	a leading space (except f=7).

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 9816. 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 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.

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