IAI America ROBO Cylinder Series - Manual (Page 37)

4. Communication
29
Modbus
4.2 Timeout and Retry
After sending a query, the host waits for a response from the controller (except when the query
that has been sent is a broadcast query).
If the elapsed time after sending a command until a response is received exceeds the timeout
value (Tout), the host may send the command again to reestablish communication. If the
number of retries exceeds three times, it means that an irremediable communication error has
occurred.
The method for calculating the timeout value (Tout) is explained below.
1. Timeout value (Tout)
Tout = To + D + (10 x Bprt/Kbr) [ms]
To : Internal processing time* x Safety factor (3)
D : Min. delay for activating local transmitter [ms]
(default value of parameter No. 17 is 5 ms)
Kbr : Baud rate [kbps]
Bprt : Response message bytes + 8
Caution The internal processing time varies depending on the category of the register
to be accessed. The processing time required for each action is listed in the
table below.
Item Maximum time [ms]
Read/write a register other than those in the low-speed memory area 1
Position data (1 position) Read 4
Position data (1 position) Write 15
Position data (1 position) Read/write 18
Position data (9 positions) Read 9
Position data (9 positions) Write 90
Position data (9 positions) Read/write 98
2. Number of Retries
Nrt = 3 (note that setting of the number of retries is mandatory)