Pressure Systems 9022 - Manual (Page 33)

Pressure Systems, Inc. NetScanner™ System (9016, 9021, & 9022) User’s Manual
www.PressureSystems.com 3 - 3
and/or decimal point, as needed).
Using brackets ( [ ] ) to show optional elements, and ellipsis ( ...) to show indefinite repetition, a
typical TCP/IP command may be viewed schematically as follows:
“c[[[[p]p]p]p][ dddd][ dddd]...]”
From this schematic, it should be clear that the command letter (c) is required, the position field
(pppp) immediately follows it, and may have 0, 1, 2, 3, or 4 characters, and there may be zero or
more datum fields ( dddd), as required. For simplicity, the variable length nature of each “ dddd”
string is not shown [with brackets] above, but the required leading space character is shown. The
position field is similarly simplified (as “pppp”) below.
A typical UDP/IP command (contained in the data field following a UDP packet header) is also a
variable length character string, but has a simpler format. Generally, it has a variable length
command string (cccccc), followed by one optional datum ( dddd) field (preceded by one space
character):
“cccccc[ dddd]”
Since there are only a few simple UDP/IP commands, all references to commands below should
assume TCP/IP commands, unless otherwise indicated.
3.1.2.2 Command Field
All NetScanner ™ System modules recognize a set of predefined commands. Most are TCP/IP
commands, having only a single alphabetic letter for a command field. These are recognized only
when a formal socket connection is established with the host computer. A few are UDP/IP
commands with a longer command field. These are recognized any time the module has power
applied. All commands are functionally summarized in the following sections and detailed in
reference Section 3.2.
3.1.2.3 Position Field
The Model 9016 Intelligent Pressure Scanner may contain up to sixteen (16) separate input/output
channels, whereas the Models 9021 and 9022 have only twelve (12) channels. When commands
affect certain channels scanned by the module, the position field is used to identify those channels
as bits in a bit map. If a channel’s corresponding bit in the position field is set to a one (1), then that