UPSD3212C Datasheet, PDF (47/152 Pages) STMicroelectronics – Flash Programmable System Devices with 8032 Microcontroller Core and 16Kbit SRAM

Figure 18. PORT Type and Description (Part 2)
In/
Symbol
Out
PORT1 <3:0>, I/O
PORT3,
PORT4<7:3,1:0>
PORT2
Circuit
UPSD3212C, UPSD3212CV
Function
Bidirectional I/O port with
internal pull-ups
Schmitt input
CMOS compatible interface
PORT1 < 7:4 > I/O
PORT4.2
I/O
Bidirectional I/O port with
internal pull-ups
Schmitt input
CMOS compatible interface
Analog input option
an_enb
Bidirectional I/O port with internal
pull-ups
Schmitt input.
TTL compatible interface
AI07428
OSCILLATOR
The oscillator circuit of the uPSD321X Devices is
a single stage inverting amplifier in a Pierce oscil-
lator configuration (see Figure 19). The circuitry
between XTAL1 and XTAL2 is basically an invert-
er biased to the transfer point. Either a crystal or
ceramic resonator can be used as the feedback el-
Figure 19. Oscillator
ement to complete the oscillator circuit. Both are
operated in parallel resonance.
XTAL1 is the high gain amplifier input, and XTAL2
is the output. To drive the uPSD321X Devices ex-
ternally, XTAL1 is driven from an external source
and XTAL2 left open-circuit.
XTAL1
XTAL2
8 to 40 MHz
XTAL1
External Clock
XTAL2
AI06620
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