PIC18F2331 MICROCHIP [Microchip Technology], PIC18F2331 Datasheet - Page 37

• Manufacturer Part Number: PIC18F2331
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D
• Manufacturer: MICROCHIP [Microchip Technology]

3.3.1
This mode is unique among the three low-power idle
modes, in that it does not disable the primary system
clock. For timing sensitive applications, this allows for
the fastest resumption of device operation with its more
accurate primary clock source, since the clock source
does not have to “warm up” or transition from another
oscillator.
PRI_IDLE mode is entered by setting the IDLEN bit,
clearing the SCS bits, and executing a SLEEP instruc-
tion. Although the CPU is disabled, the peripherals
continue to be clocked from the primary clock source
specified in Configuration Register 1H. The OSTS bit
remains set in PRI_IDLE mode (see Figure 3-3).
FIGURE 3-3:
FIGURE 3-4:
 2003 Microchip Technology Inc.
CPU Clock
Peripheral
CPU Clock
Program
Peripheral
Counter
Program
Counter
OSC1
Clock
OSC1
Clock
PRI_IDLE MODE
Q1
TRANSITION TIMING TO PRI_IDLE MODE
TRANSITION TIMING FOR WAKE FROM PRI_IDLE MODE
Wake Event
Q2
PC
PC
CPU Start-up Delay
Q3
Q4
PIC18F2331/2431/4331/4431
Preliminary
Q1
PC + 2
When a wake event occurs, the CPU is clocked from the
primary clock source. A delay of approximately 10 s is
required between the wake event and when code exe-
cution starts. This is required to allow the CPU to
become ready to execute instructions. After the wake-
up, the OSTS bit remains set. The IDLEN and SCS bits
are not affected by the wake-up (see Figure 3-4).
Q1
Q2
PC + 2
Q3
DS39616B-page 35
Q4