PIC16F676-I/ST Microchip Technology Inc., PIC16F676-I/ST Datasheet - Page 58

• Manufacturer Part Number: PIC16F676-I/ST
• Description: 14 PIN, 1.75 KB FLASH, 64 RAM, 12 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F676-I/ST

• Comparators: 1
• Cpu Speed: 5 MIPS
• Eeprom Memory: 128 Bytes
• Input Output: 12
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 14-pin TSSO
• Programmable Memory: 1.75K Bytes
• Ram Size: 64 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC16F630/676
9.2.3
For applications where a clock is already available
elsewhere, users may directly drive the PIC16F630/
676 provided that this external clock source meets the
AC/DC timing requirements listed in Section 12.0.
Figure 9-2 shows how an external clock circuit should
be configured.
9.2.4
For applications where precise timing is not a
requirement, the RC oscillator option is available. The
operation and functionality of the RC oscillator is
dependent upon a number of variables. The RC
oscillator frequency is a function of:
• Supply voltage
• Resistor (R
• Operating temperature.
The oscillator frequency will vary from unit to unit due
to normal process parameter variation. The difference
in lead frame capacitance between package types will
also affect the oscillation frequency, especially for low
C
tolerance of the external R and C components.
Figure 9-3 shows how the R/C combination is
connected.
Two options are available for this Oscillator mode
which allow RA4 to be used as a general purpose I/O
or to output F
FIGURE 9-3:
DS40039C-page 56
C
EXT
R
V
EXT
SS
EXT
F
values. The user also needs to account for the
V
OSC
DD
/4
EXTERNAL CLOCK IN
RC OSCILLATOR
EXT
OSC
RA5/OSC1/
CLKIN
RA4/OSC2/CLKOUT
) and capacitor (C
/4.
RC OSCILLATOR MODE
PIC16F630/676
EXT
) values
Internal
Clock
9.2.5
When calibrated, the internal oscillator provides a fixed
4 MHz (nominal) system clock. See Electrical
Specifications,
variation over voltage and temperature.
Two options are available for this Oscillator mode
which allow RA4 to be used as a general purpose I/O
or to output F
9.2.5.1
A calibration instruction is programmed into the last
location of program memory. This instruction is a
RETLW XX, where the literal is the calibration value.
The literal is placed in the OSCCAL register to set the
calibration of the internal oscillator. Example 9-1
demonstrates how to calibrate the internal oscillator.
For best operation, decouple (with capacitance) V
and V
EXAMPLE 9-1:
9.2.6
The PIC16F630/676 devices can be configured to
provide a clock out signal in the INTOSC and RC
Oscillator modes. When configured, the oscillator
frequency divided by four (F
RA4/OSC2/CLKOUT pin. F
purposes or to synchronize other logic.
Note:
bsf
call
movwf
bcf
SS
as close to the device as possible.
Erasing the device will also erase the pre-
programmed internal calibration value for
the internal oscillator. The calibration value
must be saved prior to erasing part as
specified in the PIC16F630/676 Program-
ming specification. Microchip Develop-
ment Tools maintain all calibration bits to
factory settings.
INTERNAL 4 MH
CLKOUT
STATUS, RP0
3FFh
OSCCAL
STATUS, RP0
OSC
Calibrating the Internal Oscillator
Section 12.0,
/4.
CALIBRATING THE
INTERNAL OSCILLATOR
 2003 Microchip Technology Inc.
OSC
OSC
Z
;Bank 1
;Get the cal value
;Calibrate
;Bank 0
/4 can be used for test
OSCILLATOR
for
/4) is output on the
information
DD
on