90 Appendix B
Network Points
RAM Variables
RAM variables use the Modbus command 04 Read Input Registers. RAM variables are read only
variables that correspond to what is shown on Digital Interface Module (DIM) display. TSI offers a
number of different models, so if a feature is not available on a unit, the variable is set to 0.
Information Provided to Master
System
Integer DDC system receives
Displayed in in. W.C.
Host DDC system must
divide value by 10,000 to
report pressure correctly
Displayed in number per hour.
Host DDC system must
divide value by 10 to report
ACH correctly.
Displayed in °F
Host DDC system must
divide value by 10 to report
temperature correctly
Displayed in in. W.C.
Host DDC system must
divide value by 100,000 to
report pressure correctly
Supply Air
Discharge
Temperature
Room 1 Supply Air Discharge
Temperature
Displayed in °F
Host DDC system must
divide value by 10 to report
temperature correctly
EXAMPLE of 04 Read Input Registers function format
This example reads variable addresses 0 (Pressure).
QUERY RESPONSE
Field Name Example # 2 Field Name Example # 1
(Hex) (Hex)
Slave Address 01 Slave Address 01
Function 04 Function 04
Starting Address Hi 00 Byte Count 02
Starting Address Lo 00 Data Hi Addr0 00
No. of Points Hi 00 Data Lo Addr0 64 (0.00100 “H
2
0)
No. of Points Lo 01
Error Check (CRC) --
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