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Z51F6412
Product Specification
PS030302-0212
P R E L I M I N A R Y
147
12.4 STOP mode
The power control register is set to ‘03h’ to enter the STOP Mode. In the stop mode, the main
oscillator, system clock and peripheral clock is stopped, but watch timer continue to operate. With the
clock frozen, all functions are stooped, but the on-chip RAM and control registers are held.
The source for exit from STOP mode is hardware reset and interrupts. The reset re-defines all the
control registers.
When exit from STOP mode, enough oscillation stabilization time is required to normal operation.
Figure 12-3 shows the timing diagram. When released from STOP mode, the Basic interval timer is
activated on wake-up. Therefore, before STOP instruction, user must be set its relevant prescaler
divide ratio to have long enough time (more than 20msec). this guarantees that oscillator has started
and stabilized.
OSC
CPU Clock
External
Interrupt
Normal Operation
BIT Counter
STOP Operation
Normal Operation
Release
STOP Instruction
Execute
Clear & Start
TST > 20ms by Software
Before executed STOP instruction, BIT must be set properly by
software to get stabilization is to be longer than 20ms.
n
n+1
N+2
n+3
FF
0
1
0
1
FE
Figure 12-3 STOP Mode Release Timing by External Interrupt
OSC
CPU Clock
/RESET
Normal Operation
BIT Counter
STOP Operation
Normal Operation
Release
Stop Instruction
Execute
Clear & Start
TST = 16ms
m-2
m-1
m
n
FF
0
1
0
1
FE
Figure 12-4 Mode Release Timing by /RESET