What are the limitations of Modbus RTU?


#1

Limitations of Modbus RTU

1.Maximum number of of devices - 32

Specification supports up to 247 slaves

Limited to 32 devices,per RS-485 standard

2.Limited distances

RS 232 - 25 ft (7.5 m)
RS 485- 4000 ft(1.2 km)

3.Data access constraints

Single modbus master support only
No provision for simultaneous SCADA /diagnostic access
Difficult to implement “bumpless” SCADA redundancy