PIC12F1822 MICROCHIP [Microchip Technology], PIC12F1822 Datasheet - Page 71

• Manufacturer Part Number: PIC12F1822
• Description: 8/14-Pin Flash Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

6.0
The reference clock module provides the ability to send
a divided clock to the clock output pin of the device
(CLKR) and provide a secondary internal clock source
to the modulator module. This module is available in all
oscillator configurations and allows the user to select a
greater range of clock submultiples to drive external
devices in the application. The reference clock module
includes the following features:
• System clock is the source
• Available in all oscillator configurations
• Programmable clock divider
• Output enable to a port pin
• Selectable duty cycle
• Slew rate control
The reference clock module is controlled by the CLKR-
CON register (Register 6-1) and is enabled when set-
ting the CLKREN bit. To output the divided clock signal
to the CLKR port pin, the CLKROE bit must be set. The
CLKRDIV<2:0> bits enable the selection of 8 different
clock divider options. The CLKRDC<1:0> bits can be
used to modify the duty cycle of the output clock
CLKRSLR bit controls slew rate limiting.
For information on using the reference clock output
with the modulator module, see Section 22.0 “Data
Signal Modulator”.
6.1
The slew rate limitation on the output port pin can be
disabled. The Slew Rate limitation can be removed by
clearing the CLKRSLR bit in the CLKRCON register.
6.2
Upon any device Reset, the reference clock module is
disabled. The user’s firmware is responsible for
initializing the module before enabling the output. The
registers are reset to their default values.
 2010 Microchip Technology Inc.
Note 1: If the base clock rate is selected without a
REFERENCE CLOCK MODULE
Slew rate
Effects of a Reset
divider, the output clock will always have
a duty cycle equal to that of the source
clock, unless a 0% duty cycle is selected.
If the clock divider is set to base clock/2,
then 25% and 75% duty cycle accuracy
will be dependent upon the source clock.
PIC12F/LF1822/16F/LF1823
(1)
. The
Preliminary
6.3
There are two cases when the reference clock output
signal cannot be output to the CLKR pin, if:
• LP, XT, or HS oscillator mode is selected.
• CLKOUT function is enabled.
Even if either of these cases are true, the module can
still be enabled and the reference clock signal may be
used in conjunction with the modulator module.
6.3.1
If LP, XT, or HS oscillator modes are selected, the
OSC2/CLKR pin must be used as an oscillator input pin
and the CLKR output cannot be enabled. See
Section 5.2 “Clock Source Types” for more informa-
tion on different oscillator modes.
6.3.2
The CLKOUT function has a higher priority than the
reference clock module. Therefore, if the CLKOUT
function is enabled by the CLKOUTEN bit in Configura-
tion Word 1, F
pin. Reference Section 4.0 “Device Configuration”
for more information.
6.4
As the reference clock module relies on the system
clock as its source, and the system clock is disabled in
Sleep, the module does not function in Sleep, even if
an external clock source or the Timer1 clock source is
configured as the system clock. The module outputs
will remain in their current state until the device exits
Sleep.
Conflicts with the CLKR pin
Operation During Sleep
OSCILLATOR MODES
CLKOUT FUNCTION
OSC
/4 will always be output on the port
DS41413A-page 71