8-32 Field Control™ Genius® Bus Interface Unit User’s Manual – October 1999 GFK-0825F
8
Read I/O Forces
Subfunction Code: 40 hex
This datagram can be used to set read force information from a Genius Bus Interface Unit. The
information read is determined by the value specified in the datagram.
Byte # Description
0 Force Table Requested: 0 = input enable
1 = output enable
2 = input value s
3 = output values
• To read which inputs are forced, specify the number 0 in the datagram.
• T o read which outputs are forced, specify 1 in the datagram.
• T o r ead forced input values, sp eci fy 2 in the datagram.
• T o r ead forced output values, sp eci fy 3 in the datagram.
In the BIU, two force enable tables show which points are forced. Two force values tables show the
forced values. Each table contains a byte of data for each byte of discrete data followed by a word
of data for each channel of analog data. For example, if a BIU is configured to have 6 bytes of
discrete input data and 6 channels of analog input data, the input force enable table and input force
value table would look like this:
Force Enabled Table Force Values Table
Byte # Description Byte # Description
0 1st 8 discrete inputs f orce enable 0 1st 8 discrete inputs force val ues
1 2nd 8 discrete inputs force enable 1 2nd 8 discrete inputs force values
2.2.
3.3.
4.4.
5 last 8 discrete inputs force enable 5 last 8 discrete inputs force values
6, 7 1st channel analog in puts force enable 6, 7 1st c hannel analog inputs force values
8, 9 2n d ch an nel analog inputs force en abl e 8, 9 2nd channel anal og in put s f orc e values
10, 11 . 10, 11 .
12, 13 . 12, 13 .
14, 15 . 14, 15 .
16, 17 6th channel an alog inputs force enab le 16, 17 6th c hannel analog inputs force value
Note that it is possible to have no discrete inputs or outputs or no analog inputs or outputs.
Read I/O Forces Reply
Subfunction Code: 41 hex
This datagram provides the information requested by a Read I/O Forces datagram.
Byte # Description
0 Force Table Requested: 0 = input enable
1 = output enable
2 = input value s
3 = output values
1 - 128 Input/Output force enable/value table data
For discrete data, a 1 in a bit position in the force enable table corresponds to an enabled force for
that point. For analog data, the value FFFF (hex) in a word position in the enable table corresponds
to an enabled force for an ana log channel.