Information

PIC16C62X
DS80101D-page 6  2004 Microchip Technology Inc.
2. Module: Oscillator
The Oscillator Start-up Timer (TOST) delay may not
occur when the device wakes up from SLEEP.
Figure 2 shows the start-up of the crystal after the
event that causes the device to wake-up from SLEEP
mode (as specified in the Device Data Sheet). The
start-up time (T
OST) may not occur.
The events that wake-up the device from SLEEP are:
• An interrupt
• A WDT overflow (wake-up)
• A Brown-out Reset
• A MCLR
Reset
FIGURE 2: WAKE-UP FROM SLEEP
In applications where time-based measurements are
started immediately after wake-up from SLEEP, the
suggested work around should be implemented.
Work around
After the SLEEP instruction, do a software delay of 256
T
CY (same as 1024 TOSC). At the RESET and Interrupt
vector addresses, test to see if the device woke from
SLEEP (the TO and PD bits), and if the device did wake
from SLEEP, ensure that the total cycle delay is 256
T
CY.
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
CLKOUT
(4)
INSTRUCTION FLOW
PC
Instruction
Fetched
Instruction
Executed
PC PC+1 —
Inst(PC) =
SLEEP
Inst(PC - 1)
Inst(PC + 1)
SLEEP
T CY T CY T CY
TOST
(2)
T CY
Note 1: For TOST delay to be enabled, the XT, HS, or LP Oscillator mode must be selected.
2: T
OST = 1024TOSC, This delay may not occur, and every valid clock edge will generate internal device clocks.
3: CLKOUT is not available in these
OSC modes, but shown here for timing reference.
Wake-up Event Occurs