SCADA polling budget (Modbus read of holding registers)

All values are your assumptions. Use a point or a comma for decimals. A comma followed by exactly three digits is read as a thousands separator (1,000 is 1000); 1.000 is rejected as ambiguous.

Devices polled (inverters)

Registers per read (1 to 125)

Link type

Baud rate

Bits per character

Devices per RS-485 line

Device response time (ms)

Network round trip (ms)

Target scan interval (s)

Illustrative only. Lines are polled in parallel; the busiest line sets the scan. Silent gaps use 3.5 character times at every baud rate; a forum quote, not the specification, says about 1.75 ms may apply above 19200 baud. Payload is raw register bytes (2 per register), not stored size. Limits of 10000 devices and 255 per line are set by this page, not by a standard.