Section A.2 - Application Notes.Design Examples
Version 1.3 - 2009-12
41
A.2.2.4 External RS422/RS485 transceiver
Note: This function is currently not supported
A complete RS422/RS485 transceiver design connected to a bus system need to control the en-
able signals of the transceiver. The SerialSelect signals are used for this purpose (see Table 12).
The module need to be software configured to the corrected interface, see the Serial Port Adap-
ter AT Commands document how to configure the module to the correct serial interface.
The Red/Mode pin is not allowed to be pull-down when using the SerialSelect signals (see sec-
tion 2.3).
Table 12: SerialSelect signals combinations
Serial
Select-0
Serial
Select-1
RS485/RS422 Transmitter
status (Active high)
RS485/RS422 Receiver
status (Active low)
0 0 Disabled
Enabled
0 1 Enabled
Enabled
1 0 Enabled
Disabled
1 1 Disabled
Disabled
Figure 16: A complete RS422/RS488 transceiver design.