Measurement Specialties 9116 - Manual (Page 29)

Pressure Systems, Inc. Model 9116 User’s Manual
Page 20 www.PressureSystems.com
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 Model 9116 scanners 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 9116 Intelligent Pressure Scanner may contain up to sixteen (16) separate
input/output 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 channel is affected by the command. The
least-significant (rightmost) bit 0 corresponds to Channel 1, and the most-significant (leftmost)
bit 15 corresponds to Channel 16. Since neither model has more than sixteen (16) channels,
the position field will usually be 16-bits, represented by four (4) ASCII-hex characters in the
command. For example, only Channels 16 and 1 are selected below in this 16-bit (4-character)
position field:
Bit# 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Chan# 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Binary 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
Hex 8 0 0 1
The above position field, with all applicable bits set (i.e., FFFF for 16-channel module), specifies
all channels. However, a module-independent variation allows a missing position field to
designate all channels — but only when there are no other parameters following the position
field in the command. For such commands, the hex position field may be reduced to 3, 2, or 1
characters when no channel bits need be set (1) in the discarded high-order characters
(nibbles).
Note
The channel data requested will always be returned in order of
highest requested channel to lowest requested channel.