Measurement Specialties 9116 user manual Command Field, Position Field

Pressure Systems, Inc. Model 9116 User’s Manual

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.

3.1.2.2Command 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.

3.1.2.3Position 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#

Chan#

Binary

Hex

15	14	13		12	11	10	9		8	7	6	5		4	3	2	1		0
16	15	14		13	12	11	10		9	8	7	6		5	4	3	2		1
1	0		0	0	0	0		0	0	0	0		0	0	0	0		0	1
		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.

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