![US Robotics Courier USR3500 Reference Manual Download Page 23](http://html1.mh-extra.com/html/us-robotics/courier-usr3500/courier-usr3500_reference-manual_1063559023.webp)
Rev 1.0
1/27/14
23
23
Reference Guide
Interfaces
Figure 15. RS232 Serial Link Signals
The RS232 interface has been designed to allow flexibility in the use of the serial
interface signals. However, the use of TXD, RXD, CTS and RTS signals are
mandatory; while the use of DTR, DSR, DCD and RI signals are optional.
Tip:
The modem is designed to operate using all serial interface signals and it is recommended to use
CT105/RTS and CT106/CTS for hardware flow control in order to avoid data corruption during
transmission.
The USR3500 also implements the Serial Port Auto Shut Down feature with the DTR signal. It is
recommended to use the CT108-2/DTR signal to benefit from the current consumption
improvement performed by this feature.
3.1.2.2.
RS232 Implementation
The following subsections describe how the RS232 serial link can be implemented to
suit different designs.
3.1.2.2.1.
5-wire Serial Interface RS232 Implementation
The signals used in this interface are as follows:
•
CT103/TXD
•
CT104/RXD
•
CT105/RTS
•
CT106/CTS
•
CT108-2/DTR
Note:
The CT108-2/DTR signal must be managed following the V24 protocol signaling if the Sleep Idle
Mode and Serial Port Auto Shut Down feature are to be used.