ZBasic Language Reference
222
ZBasic Microcontrollers
The first alternate above is similar to the circuitry used on the ZX-24 series devices. The advantage to
this circuit is its simplicity. The disadvantage is that the voltage levels of the serial output signal do not
meet the RS-232 standard. Even so, most serial receivers are able to properly interpret the output signal.
Note that if the inverters used have protection diodes on their inputs the external diodes shown are not
necessary.
The second alternate serial interface is shown in the diagram below. This circuit produces a serial output
signal that meets the RS-232 standard by using the negative voltage on the receive line to provide a
reference for the output level. Although the parts count is higher, the circuit uses inexpensive and non-
critical components.
Alternate Serial Interface Circuit #2
Reset Circuit
You may also want to incorporate a reset button in your circuitry. If so, a normally open, momentary
contact switch may be connected directly between the /RST pin of the AVR and ground. If other circuitry
in your application also needs the reset signal, you may want to isolate that circuitry from the ATN resets
(if using the ZBasic bootloader) by using a buffer gate or a diode. A suggested diode isolation circuit for
the reset line is shown below.
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