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4.4
IO Expansion Mechanism
If the application is to implement physical switches for network configuration, but does not have
sufficient I/O pins, the switches can be connected to the Anybus CompactCom instead using the
IO Expansion Mechanism. The INPUT1 and INPUT2 pins can then be used both to strap the
Modbus communication settings and to connect the physical switches.
The Anybus CompactCom will sample the INPUT1 and INPUT2 pins to determine the Modbus
communication settings before Modbus communication is performed. When the first Modbus
telegram has been exchanged, the DE signal can be used to alter the INPUT1 and INPUT2 signals
to sample the physical switches. The application processor can then read the INPUT1 and INPUT2
pins in Modbus register 0x0FFD (Anybus switch status) and write back the values to Modbus
registers 0x5200 (Application switch 1) and 0x5201 (Application switch 2).
Anybus
®
CompactCom
™
B40 Modbus Serial User Manual
SCM-1202-130 1.1 en-US