Datasheet

PIC16HV540
DS40197B-page 34 Preliminary  2000 Microchip Technology Inc.
The Electrical Specifications sections show RC fre-
quency variation from part to part due to normal pro-
cess variation. The variation is larger for larger R (since
leakage current variation will affect RC frequency more
for large R) and for smaller C (since variation of input
capacitance will affect RC frequency more).
Also, see the Electrical Specifications sections for vari-
ation of oscillator frequency due to V
DD for given Rext/
Cext values as well as frequency variation due to oper-
ating temperature for given R, C, and V
DD values.
When used in RC mode, the CLKOUT pin can be used
as a programmable clock output. The output is
connected to TMR0, bit 0, and by setting the prescaler
rate select bits, clock out frequencies of CLKIN/8 to
CLKIN/1024 can be generated.
FIGURE 7-5: RC OSCILLATOR MODE
7.3 Reset
PIC16HV540 devices may be reset in one of the follow-
ing ways:
• Power-On Reset (POR)
• MCLR
reset (normal operation)
• MCLR wake-up reset (from SLEEP)
• WDT reset (normal operation)
• WDT wake-up reset (from SLEEP)
• Wake-up from SLEEP on Pin Change
• Brown-out Detect
Table 7-3 shows these reset conditions for the PCL and
STATUS registers.
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), MCLR
or WDT
Reset. A MCLR
, WDT Wake-up from SLEEP or Wake-
up from SLEEP on Pin Change also results in a device
RESET, and not a continuation of operation before
SLEEP.
The TO
and PD bits (STATUS <4:3>) and PCWUF
(STATUS<7>) are set or cleared depending on the dif-
ferent reset conditions (Section 7.9). These bits may be
used to determine the nature of the reset.
Table 7-4 lists a full description of reset states of all reg-
isters. Figure 7-6 shows a simplified block diagram of
the on-chip reset circuit.
Note: If you change from this device to another
device, please verify oscillator characteris-
tics in your application.
VDD
REXT
CEXT
VSS
OSC1
Internal
clock
OSC2/CLKOUT
TMR0, 0
PIC16HV540
N