UPSD3254 STMICROELECTRONICS [STMicroelectronics], UPSD3254 Datasheet - Page 50

• Manufacturer Part Number: UPSD3254
• Description: Flash Programmable System Devices with 8032 Microcontroller Core
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

UPSD3254A, UPSD3254BV, UPSD3253B, UPSD3253BV
OSCILLATOR
The oscillator circuit of the uPSD325X devices is a
single stage inverting amplifier in a Pierce oscilla-
tor 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 uPSD325X devices.
Figure 20. RESET Configuration
50/175
Via the external RESET pin
Via the internal LVR Block.
Reset
USB Reset
WDT
LVR
RSTE
XTAL1
8 to 40 MHz
Timer
10ms
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 uPSD325X devices ex-
ternally, XTAL1 is driven from an external source
and XTAL2 left open-circuit.
The RESET mechanism is illustrated in Figure 20.
Via USB bus reset signaling.
Via Watch Dog timer
XTAL1
External Clock
Clock
CPU
Sync
XTAL2
“ Active Low
PERI.
CPU
&
PSD_RST
AI06621
AI06620