The schematic below is used to make a half duplex RS232 monitoring cable.
This cable is used for monitoring 2 devices that send data in half duplex. For example, one device sends data and another devices wait for incoming data. In the half duplex mode both devices cannot transmit at the same time. If it will be happened the data would be unreadable. This mode is used in all master-slave applications. In this mode the computer (P3) cannot send data and interfere in data exchange between external devices.
Advanced Serial Port Monitor can be used to
receive either ASCII or Hex half duplex data.
The following cable is used for monitoring full duplex RS232 communication.
This cable is used when you need to monitor data exchange between two external devices that may transmit async data (full duplex mode). You need 2 RS232 ports on your computer (an individual port for outgoing and incoming data). Advanced Serial Port Monitor can display
both sides of full duplex RS232 communication in the "Dual ports" mode. In this mode the computer (P3, P4) cannot send data and interfere in data exchange between external devices.