UPSD3234AV-24U1T STMicroelectronics, UPSD3234AV-24U1T Datasheet - Page 45

• Manufacturer Part Number: UPSD3234AV-24U1T
• Description: Flash Programmable System Devices with 8032 Microcontroller Core and 64Kbit SRAM
• Manufacturer: STMicroelectronics

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OSCILLATOR
The oscillator circuit of the uPSD323X Devices is
a single stage inverting amplifier in a Pierce oscil-
lator configuration. The circuitry between XTAL1
and XTAL2 is basically an inverter biased to the
transfer point. Either a crystal or ceramic resonator
can be used as the feedback element to complete
Figure 19. Oscillator
SUPERVISORY
There are four ways to invoke a reset and initialize
the uPSD323X Devices.
Figure 20. RESET Configuration
Via the external RESET pin
Via the internal LVR Block.
Via USB bus reset signaling.
Via Watch Dog timer
Reset
USB Reset
WDT
LVR
RSTE
XTAL1
8 to 40 MHz
Timer
10ms
uPSD3234A, uPSD3234BV, uPSD3233B, uPSD3233BV
XTAL2
Cancel
Noise
10ms at 40Mhz
50ms at 8Mhz
S
R
Q
the oscillator circuit. Both are operated in parallel
resonance.
XTAL1 is the high gain amplifier input, and XTAL2
is the output. To drive the uPSD323X Devices ex-
ternally, XTAL1 is driven from an external source
and XTAL2 left open-circuit.
The RESET mechanism is illustrated in Figure 20.
Each RESET source will cause an internal reset
signal active. The CPU responds by executing an
internal reset and puts the internal registers in a
defined state. This internal reset is also routed as
an active low reset input to the PSD Module.
XTAL1
External Clock
Clock
CPU
Sync
XTAL2
“ Active Low
PERI.
CPU
&
PSD_RST
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