Spectrum Controls InView Series User Manual page 78

4-14 Chapter 4: InView Protocol
Beg of
ADDR
Frame
: FF
User's Manual 0300277-02 Rev. D
Examples of Modbus ASCII Functions
The following sections show examples of Modbus ASCII protocol
Query/Response transmissions to/from a display for each command instruction
listed above. Modbus ASCII will write/read to the holding registers in the
display. These registers are in the 40000 range. When writing to register 40101,
40001 is dropped from the address leaving 100 (0×64). The following example
shows the transmission of data to holding register 40102 in all displays. The
display adds 40001 to the starting address upon receiving the transmission before
updating the appropriate holding register.
Example of a Target Holding Register
H.O
FUNC
ADDR
06 00
Target holding register 40102 – 40001 = 101 (0×65)
Format for the following sections is the use of a query/response or a
transmission. Each section shows the complete transmission and response (if
applicable). In some examples, there are multiple steps that are needed to
complete the function requested. Within these steps, there are pause or delay
times that must be used in-between each step.
The data that is sent is ASCII information and the CR and LF represents 0×0d
and 0×0a respectively. The beginning of frame (:) represents (03a).
Heartbeat Function
The heartbeat function, when enabled, allows the display to determine if it is no
longer on the network or if the host device is not functioning properly (not
sending data or a heartbeat). Should the display not see any serial activity (valid
or invalid) within 3 seconds, an error message No Network Activity is displayed.
The heartbeat is either enabled or disabled via protocol or software.
Factory Default: DISABLED.
Enable the Heartbeat Function
The displays are shipped with the heartbeat disabled. Should the heartbeat
function be required, the following string of information enables the display to
look for a heartbeat or serial activity.
Transmission is as follows:
L.O
DATA
ADDR
65 FFFF
Ready to
LRC
EOF rec.
Error
response
98 CR LF