Manual USB-FLEXCOM4
7
COM Port Compatibility
The FT4232H is FTDI’s fifth generation of USB devices. It generates a USB protocol engine
which controls the physical universal transceiver macro cell interface and handles all
aspects of the USB 2.0 high speed interface. It also includes 2K bytes TX & RX data buffers
per port.
The driver/receiver used (SP491 in non-RS232 modes) is capable of driving extremely long
communication lines at high baud rates. It can drive up to +60 mA on balanced lines and
receive inputs as low as 200 mV differential signal superimposed on common mode noise of
+12 V to -7 V. In case of communication conflict, the driver/receivers feature thermal
shutdown. The driver/receiver used in RS232 mode is the ICL3243.
Communication Mode
The board supports Half-Duplex communications with a 2-wire cable connection. Half-
Duplex allows traffic to travel in both directions, but only one way at a time. RS485
communications commonly use the Half-Duplex mode since they share only a single pair of
wires. RS-232 suffers from a maximum usable distance of 50 feet, as only one side of the
line is actively driven with a common return. RS-422 and RS-485 are both capable of
operating without error at up to 4000 feet as both communication lines are actively driven
instead of just one as in RS-232.
Half-Duplex mode:
RS-485 multi-drop (32 transmitters/receivers allowed on a single twisted pair)
Full-Duplex modes:
RS-422
RS-232
Differential communication modes:
RS-485
RS-422
Single-ended communication mode:
RS-232