PIC16C72_13 Datasheet, PDF (61/128 Pages) Microchip Technology – 8-Bit CMOS Microcontrollers with A/D Converter

10.2.3 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 (REXT) 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
CEXT values. The user also needs to take into account
variation due to tolerance of external R and C compo-
nents used. Figure 10-4 shows how the R/C combina-
tion is connected to the PIC16CXXX family.
FIGURE 10-4: RC OSCILLATOR MODE
VDD
Rext
OSC1
Internal
clock
Cext
PIC16CXXX
VSS
OSC2/CLKOUT
Fosc/4
Recommended values: 3 k  Rext  100 k
Cext > 20pF
PIC16C72 Series
10.3 Reset
The PIC16CXXX family differentiates between various
kinds of reset:
• Power-on Reset (POR)
• MCLR reset during normal operation
• MCLR reset during SLEEP
• WDT Reset (normal operation)
• 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 differ-
ently in different reset situations as indicated in
Table 10-4. These bits are used in software to deter-
mine the nature of the reset. See Table 10-6 for a full
description of reset states of all registers.
A simplified block diagram of the on-chip reset circuit is
shown in Figure 10-5.
The PIC16C72/CR72 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.
 1998-2013 Microchip Technology Inc.
Preliminary
DS39016B-page 61