HMS Anybus CompactCom B40 Modbus Serial User Manual page 19

Hardware Design
4.1.3 Settings
Signal Name
OM3
OM2
OM1
OM0
MI0
MI1
MD0
RX
TX
Module Detection
This signal is internally connected to GND, and can be used by the host application to detect
whether a module is present or not. When connecting an external pull-up resistor, a low signal
indicates that a module is present.
If not used, leave this signal unconnected.
4.1.4 DE (Data Enable)
The Anybus CompactCom B40 Modbus Serial supports RS485. This signal is then used as an
active high data enable signal for RS485 transceivers.
Signal Name
DE
This signal must be pulled to GND on the host application side to prevent spurious transmissions
during startup.
Anybus ® CompactCom ™ B40 Modbus Serial User Manual
Type
Pin
I 52
I 35
I 33
I 32
O 54
O 53
O 30
I 51
O 52
Pin Type Pin
O 38
Description
Set [OM3, OM2, OM1, OM0] to [0,0,1,1] for Modbus Serial
operation.
OM3 is used to set operation mode at startup, and requires a
pull-down resistor. It is used as TX output after startup. The pull-
down resistor shall have a value between 1 kΩand 2.2 kΩ.
[MI1, MI0] = [1,0] indicates that the Anybus CompactCom
connected comes from the Anybus CompactCom 40-series..
Module Detection
This signal can be used by the host application to determine that
an Anybus CompactCom is inserted into the slot, see
Detection, p. 17.
The signal is connected directly to GND on the Anybus
CompactCom.
Serial Communications Signals, used for Modbus Communication.
TX is used as OM3 during setup
Description
Data Enable
Active high signal used for RS485 transceiver.
17 (48)
Module
SCM-1202-130 1.1 en-US