PIC16C63A Microchip Technology, PIC16C63A Datasheet - Page 83

• Manufacturer Part Number: PIC16C63A
• Description: 28/40-Pin 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

11.2.3
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
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
variation due to tolerance of external R and C compo-
nents used. Figure 11-4 shows how the R/C combina-
tion is connected to the PIC16CXXX.
FIGURE 11-4: RC OSCILLATOR MODE
EXT
Cext
V
Recommended values: 3 k
1998 Microchip Technology Inc.
Rext
SS
EXT
values. The user also needs to take into account
V
DD
RC OSCILLATOR
) and capacitor (C
Fosc/4
OSC1
OSC2/CLKOUT
Cext > 20pF
EXT
) values and the operat-
Rext
100 k
PIC16CXXX
Internal
clock
PIC16C63A/65B/73B/74B
11.3
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 differ-
ently in different reset situations as indicated in
Table 11-4. These bits are used in software to deter-
mine the nature of the reset. See Table 11-6 for a full
description of reset states of all registers.
A simplified block diagram of the on-chip reset circuit is
shown in Figure 11-5.
The PICmicros 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.
Reset
DS30605A-page 83