W78E516B
6.6 Power Management
Idle Mode
Setting the IDL bit in the PCON register enters the idle mode. In the idle mode, the internal clock to the
processor is stopped. The peripherals and the interrupt logic continue to be clocked. The processor
will exit idle mode when either an interrupt or a reset occurs.
Power-down Mode
When the PD bit in the PCON register is set, the processor enters the power-down mode. In this mode
all of the clocks are stopped, including the oscillator. To exit from power-down mode is by a hardware
reset or external interrupts INT0 to INT1 when enabled and set to level triggered.
6.7 Reduce EMI Emission
The W78E516B allows user to diminish the gain of on-chip oscillator amplifier by using programmer to
clear the B7 bit of security register. Once B7 is set to 0, a half of gain will be decreased. Care must be
taken if user attempts to diminish the gain of oscillator amplifier, reducing a half of gain may affect the
external crystal operating improperly at high frequency above 24 MHz. The value of R and C1, C2
may need some adjustment while running at lower gain.
6.8 Reset
The external RESET signal is sampled at S5P2. To take effect, it must be held high for at least two
machine cycles while the oscillator is running. An internal trigger circuit in the reset line is used to
deglitch the reset line when the W78E516B is used with an external RC network. The reset logic also
has a special glitch removal circuit that ignores glitches on the reset line. During reset, the ports are
initialized to FFH, the stack pointer to 07H, PCON (with the exception of bit 4) to 00H, and all of the
other SFR registers except SBUF to 00H. SBUF is not reset.
W78E516B Special Function Registers (SFRs) and Reset Values
F8
F0
E8
E0
D8
D0
C8
C0
B8
B0
+ACC
00000000
+P4
xxxx1111
+PSW
00000000
+T2CON
00000000
XICON
00000000
+IP
00000000
+P3
00000000
+B
00000000
CHPENR
00000000
FF
F7
EF
E7
DF
D7
RCAP2L
00000000
P4CONA
00000000
RCAP2H
00000000
P4CONB
00000000
TL2
00000000
SFRAL
00000000
TH2
00000000
SFRAH
00000000
CF
SFRFD
00000000
SFRCN
00000000
CHPCON
0xx00000
C7
BF
B7
P43AL
00000000
P43AH
00000000
-8-
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