RS232 interface circuits for 3.3V systems are described.
RS232 interface circuit
The rapid, widespread use of 3.3V logic circuits complicates the selection of RS232 interface circuits. The optimum choice of an interface circuit should be based upon several application dependent factors:
1) Logic circuitry connected to interface chip
2) Power supply voltages available
3) Power consumption constraints
4) Serial interface environment
5) Mouse driving requirements
As Figure 396.1 illustrates, 5V interface circuits cannot be used to directly connect to 3.3V CMOS logic circuits. The receiver output level will forward ...