HMS87C1808B Datasheet, PDF (72/99 Pages) List of Unclassifed Manufacturers – 8-BIT SINGLE-CHIP MICROCONTROLLERS

HMS87C1X04B/08B/16B
Release the STOP mode
The exit from STOP mode is hardware reset or external interrupt.
Reset re-defines all the Control registers but does not change the
on-chip RAM. External interrupts allow both on-chip RAM and
Control registers to retain their values. If I-flag = 1, the normal in-
terrupt response takes place. If I-flag = 0, the chip will resume ex-
ecution starting with the instruction following the STOP
instruction. It will not vector to interrupt service routine. (refer to
Figure 18-1 )
By reset, exit from Stop mode is shown in Figure 18-3 .When exit
from Stop mode by external interrupt, enough oscillation stabili-
zation time is required to normal operation. Figure 18-2 shows
the timing diagram. When release the Stop mode, the Basic inter-
val timer is activated on wake-up. It is increased from 00_H until
FF_H . The count overflow is set to start normal operation. There-
fore, before STOP instruction, user must be set its relevant pres-
caler divide ratio to have long enough time (more than 20msec).
This guarantees that oscillator has started and stabilized..
STOP
INSTRUCTION
STOP Mode
Interrupt Request
Corresponding Interrupt
Enable Bit (IENH, IENL)
IEXX
=0
=1
STOP Mode Release
Master Interrupt
Enable Bit PSW[2]
I-FLAG
=0
=1
Interrupt Service Routine
Next
INSTRUCTION
Figure 18-1 STOP Releasing Flow by Interrupts
Oscillator
(X_IN pin)
Internal
Clock
External
Interrupt
BIT
Counter
STOP Instruction Execution
N-2 N-1 N N+1
Normal Operation
N+2
STOP Mode
Clear Basic Interval Timer
00 01
FE FF 00 00
Stabilizing Time
t_ST > 20mS
Normal Operation
Figure 18-2 Timing of STOP Mode Release by External Interrupt
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SEP. 2004 Ver 1.03