CC864-DUAL Hardware User Guide
1vv0300791 Rev 4.4 – 2011-01-26
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Page 38 of 63
NOTE:
In this case Vin has to be set with a value compatible with the logic levels of
the module. In this configuration the SP3282EB will adhere to EIA/TIA-562 voltage
levels instead of RS232 (-5 +5V)
NOTE:
The digital input lines working at 2.6V CMOS have an absolute maximum
input voltage of 2.9V; therefore the level translator IC shall not be powered by the
+3.8V supply of the module. Instead, it must be powered from a +2.6V (preferably
dedicated) power supply.
If supplied from the main 3.8V, the level translator IC outputs on the module side (i.e.
the CC864-DUAL inputs) will work at +3.8V interface levels, stressing the module
inputs beyond their maximum input voltage range.
The RS232 serial port lines are usually connected to a DB9 connector with the layout
shown in the following figure:
3.8.1.3.
5V UART Level Translation
If the host application uses a microcontroller with a serial port (UART) that works at a
voltage different from 2.6~2.9V, circuitry must be provided to translate the different
levels of the two signal sets.
As for the RS232 translation, there is a selection of single chip translators, but since
the translation requires very few components a discrete design can also be used.
The following example illustrates a potential inexpensive translator circuit for a 5V
transmitter/receiver:
