PIC12C672T-04I/SM Microchip Technology, PIC12C672T-04I/SM Datasheet - Page 48

• Manufacturer Part Number: PIC12C672T-04I/SM
• Description: IC MCU OTP 2KX14 A/D 8-SOIJ
• Manufacturer: Microchip Technology
• Series: PIC® 12Cr

Specifications of PIC12C672T-04I/SM

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 4MHz
• Peripherals: POR, WDT
• Number Of I /o: 5
• Program Memory Size: 3.5KB (2K x 14)
• Program Memory Type: OTP
• Ram Size: 128 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Data Converters: A/D 4x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (5.3mm Width), 8-SOP, 8-SOEIAJ
• For Use With: XLT08SO-1 - SOCKET TRANSITION 8SOIC 150/208AC164312 - MODULE SKT FOR PM3 16SOIC309-1048 - ADAPTER 8-SOIC TO 8-DIP309-1047 - ADAPTER 8-SOIC TO 8-DIP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Connectivity: -

PICmicro MID-RANGE MCU FAMILY
2.8
DS31002A-page 2-18
Design Tips
Question 1:
Answer 1:
1.
2.
3.
4.
Question 2:
Answer 2:
The gain is too high for this oscillator circuit. Refer to subsection
Ceramic Resonators”
and clock mode (wrong mode may be selected). This is especially possible for low frequency
crystals, like the common 32.768 kHz.
Question 3:
Answer 3:
Changing the value of C1 has some affect on the oscillator frequency. If a SERIES resonant crys-
tal is used, it will resonate at a different frequency than a PARALLEL resonant crystal of the same
frequency call-out.
Question 4:
Answer 4:
Other than the obvious software checks that should be done to investigate losing time, it is pos-
sible that the amplitude of the oscillator output is not high enough to reliably trigger the oscillator
input.
Question 5:
Answer 5:
If the frequency of the device does not matter, you can continue to use the device.
If the frequency of the device does matter, you can purchase a new windowed device, or follow
the suggestion in subsection
Executing a SLEEP instruction with no source for wake-up (such as, WDT, MCLR, or an
Interrupt). Verify that the code does not put device to sleep without providing for wake-up.
If it is possible, try waking it up with a low pulse on MCLR. Powering up with MCLR held
low will also give the crystal oscillator more time to start-up, but the Program Counter will
not advance until the MCLR pin is high.
The wrong clock mode is selected for the desired frequency. For a blank device, the
default oscillator is EXTRC. Most parts come with the clock selected in the default RC
mode, which will not start oscillation with a crystal or resonator. Verify that the clock mode
has been programmed correctly.
The proper power-up sequence has not been followed. If a CMOS part is powered through
an I/O pin prior to power-up, bad things can happen (latch up, improper start-up etc.) It is
also possible for brown-out conditions, noisy power lines at start-up, and slow V
times to cause problems. Try powering up the device with nothing connected to the I/O,
and power-up with a known, good, fast-rise, power supply. It is not as much of a problem
as it may sound, but the possibility exists. Refer to the power-up information in the device
data sheet for considerations on brown-out and power-up sequences.
The C1 and C2 capacitors attached to the crystal have not been connected properly or are
not the correct values. Make sure all connections are correct. The device data sheet val-
ues for these components will almost always get the oscillator running, they just might not
be the optimal values for your design.
When looking at the OSC2 pin after power-up with an oscilloscope, there is
no clock. What can cause this?
The PICmicro starts, but runs at a frequency much higher than the resonant
frequency of the crystal.
The design runs fine, but the frequency is slightly off, what can be done to
adjust this?
The board works fine, then suddenly quits, or loses time.
I’m using a device with the internal RC oscillator and I have accidently
erased the calibration value. What can I do?
to aid in the selection of C2 (may need to be higher) Rs (may be needed)
2.5.1 “Clock Out.”
1997 Microchip Technology Inc.
2.3 “Crystal Oscillators /
DD
rise