PIC16F946-E/PT Microchip Technology, PIC16F946-E/PT Datasheet - Page 75

• Manufacturer Part Number: PIC16F946-E/PT
• Description: Microcontroller
• Manufacturer: Microchip Technology
• Series: PIC® 16Fr

Specifications of PIC16F946-E/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 14KB (8K x 14)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 336 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 64-TFQFP
• Processor Series: PIC16F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 352 B
• Interface Type: SSP, I2C, AUSART, SPI
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 53
• Number Of Timers: 3
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, ICE2000, MA160011
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MA160011 - DAUGHTER BOARD PICDEM LCD 16F91X
• Lead Free Status / Rohs Status: Details

4.2
Clock source modes can be classified as external or
internal.
• External clock modes rely on external circuitry for
• Internal clock sources are contained internally
The system clock can be selected between external or
internal clock sources via the System Clock Selection
(SCS) bit (see Section 4.5 “Clock Switching”).
4.3
4.3.1
If the PIC16F946 is configured for LP, XT or HS modes,
the Oscillator Start-up Timer (OST) counts 1024 oscil-
lations from the OSC1 pin, following a Power-on Reset
(POR), and the Power-up Timer (PWRT) has expired (if
configured), or a wake-up from Sleep. During this time,
the program counter does not increment and program
execution is suspended. The OST ensures that the
oscillator circuit, using a quartz crystal resonator or
ceramic resonator, has started and is providing a stable
system clock to the PIC16F946. When switching
between clock sources a delay is required to allow the
new clock to stabilize. These oscillator delays are
shown in Table 4-1.
© 2005 Microchip Technology Inc.
the clock source. Examples are oscillator modules
(EC mode), quartz crystal resonators or ceramic
resonators (LP, XT and HS modes), and
Resistor-Capacitor (RC mode) circuits.
within the PIC16F946. The PIC16F946 has two
internal oscillators: the 8 MHz High-Frequency
Internal Oscillator (HFINTOSC) and 31 kHz
Low-Frequency Internal Oscillator (LFINTOSC).
Clock Source Modes
External Clock Modes
OSCILLATOR START-UP TIMER
(OST)
Preliminary
4.3.1.1
An exception to this is when the device is put to Sleep
while the following conditions are true:
• LP is the selected primary oscillator mode.
• T1OSCEN = 1 (Timer1 oscillator is enabled).
• SCS = 0 (oscillator mode is defined by
• OSTS = 1 (device is running from primary system
For this case, the OST is not necessary after a wake-up
from Sleep, since Timer1 continues to run during Sleep
and uses the same LP oscillator circuit as its clock
source. For these devices, this case is typically seen
when the LCD module is running during Sleep.
In applications where the OSCTUNE register is used to
shift the F
expect the F
In this case, the frequency may shift gradually toward
the new value. The time for this frequency shift is less
than eight cycles of the base frequency.
Table 4-1 shows examples where the oscillator delay is
invoked.
In order to minimize latency between external oscillator
start-up and code execution, the Two-Speed Clock
Start-up mode can be selected (see Section 4.6
“Two-Speed Clock Start-up Mode”).
FOSC<2:0>).
clock).
Note:
INTOSC
When the OST is invoked, the WDOG is
held in Reset, because the WDOG ripple
counter is used by the OST to perform the
oscillator delay count. When the OST
count has expired, the WDOG will begin
counting (if enabled).
INTOSC
Special Case
frequency, the application should not
frequency to stabilize immediately.
PIC16F946
DS41265A-page 73