Datasheet

PIC16C712/716
DS41106C-page 54  1999-2013 Microchip Technology Inc.
9.2.3 RC OSCILLATOR
For timing insensitive applications, the “RC” device
option offers additional cost savings. The RC oscillator
frequency is a function of the supply voltage, the resis-
tor (R
EXT) and capacitor (CEXT) values and the operat-
ing temperature. In addition to this, the oscillator
frequency will vary from unit-to-unit due to normal pro-
cess parameter variation. Furthermore, the difference
in lead frame capacitance between package types will
also affect the oscillation frequency, especially for low
C
EXT values. The user also needs to take into account
variation due to tolerance of external R and C
components used. Figure 9-4 shows how the R/C
combination is connected to the PIC16CXXX.
FIGURE 9-4: RC OSCILLATOR MODE
9.3 Reset
The PIC16CXXX differentiates between various kinds
of Reset:
• Power-on Reset (POR)
•MCLR
Reset during normal operation
•MCLR
Reset during Sleep
• WDT Reset (during normal operation)
• WDT Wake-up (during Sleep)
• Brown-out Reset (BOR)
Some registers are not affected in any Reset condition;
their status is unknown on POR and unchanged in any
other Reset. Most other registers are reset to a “Reset
state” on Power-on Reset (POR), on the MCLR
and
WDT Reset, on MCLR
Reset during Sleep and Brown-
out Reset (BOR). They are not affected by a WDT
Wake-up, which is viewed as the resumption of normal
operation. The TO
and PD bits are set or cleared
differently in different Reset situations as indicated in
Table 9-4. These bits are used in software to determine
the nature of the Reset. See Table 9-6 for a full
description of Reset states of all registers.
A simplified block diagram of the on-chip Reset circuit
is shown in Figure 9-6.
The PIC microcontrollers have a MCLR
noise filter in
the MCLR
Reset path. The filter will detect and ignore
small pulses.
It should be noted that a WDT Reset does not drive
MCLR
pin low.
OSC2/CLKOUT
CEXT
REXT
PIC16C7XX
OSC1
F
OSC/4
Internal
Clock
VDD
VSS
Recommended values: 3 k  REXT  100 k
C
EXT > 20pF