PIC18F2450-I/ML Microchip Technology Inc., PIC18F2450-I/ML Datasheet - Page 36

• Manufacturer Part Number: PIC18F2450-I/ML
• Description: Microcontroller; 16 KB Flash; 768 RAM; 0 EEPROM; 23 I/O; 28-Pin-QFN
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F2450-I/ML

• A/d Inputs: 10-Channel, 10-Bit
• Cpu Speed: 12 MIPS
• Eeprom Memory: 0 Bytes
• Input Output: 23
• Interface: EUSART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin QFN
• Programmable Memory: 16K Bytes
• Ram Size: 768 Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 2-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F2450/4450
3.1.3
The length of the transition between clock sources is
the sum of two cycles of the old clock source and three
to four cycles of the new clock source. This formula
assumes that the new clock source is stable.
Two bits indicate the current clock source and its
status. They are:
• OSTS (OSCCON<3>)
• T1RUN (T1CON<6>)
In general, only one of these bits will be set while in a
given power-managed mode. When the OSTS bit is
set, the primary clock is providing the device clock.
When the T1RUN bit is set, the Timer1 oscillator is
providing the clock.
3.1.4
The power-managed mode that is invoked with the
SLEEP instruction is determined by the setting of the
IDLEN bit at the time the instruction is executed. If
another SLEEP instruction is executed, the device will
enter the power-managed mode specified by IDLEN at
that time. If IDLEN has changed, the device will enter
the new power-managed mode specified by the new
setting.
3.2
In the Run modes, clocks to both the core and
peripherals are active. The difference between these
modes is the clock source.
FIGURE 3-1:
DS39760A-page 34
Note:
Note 1:
Peripheral
Program
Counter
Run Modes
T1OSI
OSC1
Clock
Clock
CPU
CLOCK TRANSITIONS AND
STATUS INDICATORS
Executing a SLEEP instruction does not
necessarily place the device into Sleep
mode. It acts as the trigger to place the
controller into either the Sleep mode, or
one of the Idle modes, depending on the
setting of the IDLEN bit.
MULTIPLE SLEEP COMMANDS
Clock transition typically occurs within 2-4 T
Q1
TRANSITION TIMING FOR ENTRY TO SEC_RUN MODE
Q2
PC
Q3
Q4
Q1
1
2
Advance Information
Clock Transition
3
OSC
.
PC + 2
n-1
(1)
3.2.1
The PRI_RUN mode is the normal, full power execution
mode of the microcontroller. This is also the default
mode upon a device Reset unless Two-Speed Start-up
is enabled (see Section 18.3 “Two-Speed Start-up”
for details). In this mode, the OSTS bit is set.
3.2.2
The SEC_RUN mode is the compatible mode to the
“clock switching” feature offered in other PIC18
devices. In this mode, the CPU and peripherals are
clocked from the Timer1 oscillator. This gives users the
option of lower power consumption while still using a
high accuracy clock source.
SEC_RUN mode is entered by setting the SCS1:SCS0
bits to ‘01’. The device clock source is switched to the
Timer1 oscillator (see Figure 3-1), the primary
oscillator is shut down, the T1RUN bit (T1CON<6>) is
set and the OSTS bit is cleared.
On transitions from SEC_RUN mode to PRI_RUN, the
peripherals and CPU continue to be clocked from the
Timer1 oscillator while the primary clock is started.
When the primary clock becomes ready, a clock switch
back to the primary clock occurs (see Figure 3-2).
When the clock switch is complete, the T1RUN bit is
cleared, the OSTS bit is set and the primary clock is
providing the clock. The IDLEN and SCS bits are not
affected by the wake-up; the Timer1 oscillator
continues to run.
n
Note:
PRI_RUN MODE
SEC_RUN MODE
The Timer1 oscillator should already be
running prior to entering SEC_RUN mode.
If the T1OSCEN bit is not set when the
SCS1:SCS0 bits are set to ‘01’, entry to
SEC_RUN mode will not occur. If the
Timer1 oscillator is enabled but not yet
running, device clocks will be delayed until
the
situations, initial oscillator operation is far
from stable and unpredictable operation
may result.
Q2
oscillator
Q3
Q4
© 2006 Microchip Technology Inc.
has started.
Q1
Q2
PC + 4
Q3
In
such