1997 Dec 15
43
Philips Semiconductors
Product specification
8-bit microcontrollers
P83C524; P80C528; P83C528
15.4
Wake-up from Power-down Mode
The Power-down mode of the P83C528 can also be
terminated by any one of the two external interrupts, IE0 or
IE1. A termination with an external interrupt does not affect
the internal data memory and does not affect the Special
Function Registers (SFRs). This gives the possibility to
exit Power-down without changing the port output levels.
To terminate the Power-down mode with an external
interrupt, IE0 or IE1 must be switched to be level-sensitive
and must be enabled. The external interrupt input signal
INT0 and INT1 must be kept LOW till the oscillator has
restarted and stabilized (see Fig.21).
In order to prevent any interrupt priority problems during
wake-up, the priority of the desired wake-up interrupt
should be higher than the priorities of all other enabled
interrupt sources. The instruction following the one that put
the device into the Power-down mode will be the first one
which will be executed after an interrupt has been
serviced.
Table 29
Internal registers status after a RESET
REGISTER
CONTENTS
ACC
B
DPH, DPL
IE
IP
PCH, PCL
PCON
PSW
P0 to P3
SBUF
SCON
SP
TCON
TMOD
TH0, TL0
TH1, TL1
T2CON
TH2, TL2
RCAP2H, RCAP2L
S1BIT
S1INT
S1SCS
T3
WDCON
00H
00H
00H
0000 0000B
X000 0000B
00H
0XXX 0000B
00H
FFH
Indeterminate
00H
07H
00H
00H
00H
00H
00H
00H
00H
X000 0000B
0XXX XXXXB
XXX0 0000B
00H
A5H
Fig.21 Wake up by external interrupt input.
MBC508 - 1
oscillator stopped
oscillator start up
min. 20 ms
power down
internal timing stopped
C1
C1
C1
C2
IDLE MODE
LCALL
interrupt routine
set external
interrupt latch
INT0 / INT1
INT1 1 cycle
INT0 2 cycles
interrupts are polled