PIC16F785-I/P Microchip Technology Inc., PIC16F785-I/P Datasheet - Page 26

• Manufacturer Part Number: PIC16F785-I/P
• Description: MCU, 8-Bit, 2KW Flash, 128 RAM, 18 I/O, DIP-20
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F785-I/P

• A/d Inputs: 12-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 17
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 20-pin PDIP
• Programmable Memory: 3.5K Bytes
• Ram Size: 128 Bytes
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC16F785/HV785
3.2
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 3.5 “Clock Switching”).
TABLE 3-1:
3.3.2
The External Clock (EC) mode allows an externally
generated logic level as the system clock source.
When operating in this mode, an external clock source
is connected to OSC1 pin and the RA4 pin is available
for general purpose I/O. Figure 3-2 shows the pin
connections for EC mode.
The Oscillator Start-up Timer (OST) is disabled when
EC mode is selected. Therefore, there is no delay in
operation after a Power-on Reset (POR) or wake-up
from Sleep. Because the PIC16F785/HV785 design is
fully static, stopping the external clock input will have
the effect of halting the device while leaving all data
intact. Upon restarting the external clock, the device
will resume operation as if no time had elapsed.
DS41249D-page 24
Sleep/POR
Sleep
LFINTOSC
(31 kHz)
Sleep/POR
LFINTOSC
(31 kHz)
Note 1:
Switch From
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 PIC16F785/HV785. The PIC16F785/
HV785 has two internal oscillators; the 8 MHz
High-frequency Internal Oscillator (HFINTOSC)
and 31 kHz Low-frequency Internal Oscillator
(LFINTOSC).
Clock Source Modes
The 5 s-10 s start-up delay is based on a 1 MHz System Clock.
EC MODE
INTOSC
INTOSC
OSCILLATOR DELAY EXAMPLES
EC, RC
EC, RC
Switch
INTRC
LP, XT,
HS
To
125 kHz-8 MHz
31 kHz-20 MHz
125 kHz-8 MHz
DC – 20 MHz
DC – 20 MHz
Frequency
31 kHz
Preliminary
5 s-10 s (approx.)
1024 Clock Cycles
Oscillator Delay
CPU Start-up
1 s (approx.)
(OST)
3.3
3.3.1
When the PIC16F785/HV785 is configured for any of
the Crystal Oscillator modes (LP, XT or HS), the Oscil-
lator Start-up Timer (OST) is enabled, which extends
the Reset period to allow the oscillator additional time
to stabilize. The OST counts 1024 clock periods
present on the OSC1 pin following a Power-on Reset
(POR), a wake from Sleep, or when the Power-up
Timer (PWRT) has expired (if the PWRT is enabled).
During this time, the program counter does not incre-
ment and program execution is suspended. The OST
ensures that the oscillator circuit, using a quartz crystal
resonator or ceramic resonator, has started and is pro-
viding a stable system clock to the PIC16F785/HV785.
Table 3-1 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 3.6 “Two-
Speed Clock Start-up Mode”).
FIGURE 3-2:
Clock from
Ext. System
(1)
External Clock Modes
POR, CPU start-up is invoked to allow the
CPU to become ready for code execution.
OSCILLATOR START-UP TIMER
(OST)
Following a wake-up from Sleep mode or
RA4
EXTERNAL CLOCK (EC)
MODE OPERATION
© 2006 Microchip Technology Inc.
Comments
OSC1/CLKIN
I/O (OSC2)
PIC16F785/HV785