Information

DS80011C-page 2

1999 Microchip Technology Inc.
PIC16C773
2. Module: OSCILLATOR
The Oscillator Start-up Timer (T
OST) 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 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
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 TCY.
FIGURE 2: WAKE-UP FROM SLEEP
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
(3)
INSTRUCTION FLOW
PC
Instruction
fetched
Instruction
executed
PC PC+1 —
Inst(PC) = SLEEP
Inst(PC - 1)
Inst(PC + 1)
SLEEP
Tcy Tcy Tcy
Tost(2)
Tcy
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