![FMC Technologies Smith Meter microFlow.net Liquid Manual Download Page 28](http://html.mh-extra.com/html/fmc-technologies/smith-meter-microflow-net-liquid/smith-meter-microflow-net-liquid_manual_2312633028.webp)
Page 28 • MNFL003 ║ Issue/Rev. 0.1 (9/13)
4.7
01 Read Relay Status
Description
Reads the ON/OFF status of discrete variables in the microFlow.net Liquid. The maxi-
mum number of “coils” per response is 256 in the microFlow.net Liquid.
Query
The query message specifies the starting register and quantity of registers to be read.
There are now no variables to read from this group. If there were, this is an example of
a request to read variables 20 through 56 from microFlow.net Liquid device 17:
Query
Field Name
Example (Hex)
microFlow.net Liquid Address
0x11
Function
0x01
Starting Address Hi
0x00
Starting Address Lo
0x13
No. of Points Hi
0x00
No. of Points Lo
0x25
Error Check (CRC)
(calculated)
Response
A response message consists of a relay status packed as one relay per bit of the data
field. Status is indicated by means of the following code: 0 = OFF; 1 = ON. The first data
byte is contained in the LSB, and specifies the relay addressed in the query. All other
relays follow from “low order to high order” in subsequent bytes.
The returned relay quantity must be a multiple of eight; otherwise, it will be padded with
zeros toward the high order end of the byte. The assembled bytes of data are specified
in the byte count field.
An example of a response to the preceding query appears below.
Response
Field Name
Example (Hex)
microFlow.net Liquid Address
0x11
Function
0x01
Byte Count
0x05
Data (Relays 27-20)
0xCD
Data (Relays 35-28)
0x6B
Data (Relays 43-36)
0xB2
Data (Relays 51-44)
0x0E
Data (Relays 56-52)
0x1B
Error Check (CRC)
(calculated)
The status of relays 27 through 20 is shown as the byte value CD hex, or binary 1100
1101. Relay 27 is the MSB of the byte, and relay 20 is the LSB. The status of relays
27 through 20 is expressed from left to right as ON-ON-OFF-OFF-ON-ON-OFF-ON.
Bits within a byte are shown with the MSB to the left and the LSB to the right; therefore,
the relays in the first byte are “27 through 20,” from left to right. Relays “35 through 28"
microFlow.net Liquid Modbus Communications Manual
Appendix