w78l812a Winbond Electronics Corp America, w78l812a Datasheet - Page 14

• Manufacturer Part Number: w78l812a
• Description: 8-bit Mcu Series 80c51-based
• Manufacturer: Winbond Electronics Corp America

W78LE812/W78L812A
5.8.2
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.
5.9
AUXR - Auxiliary Register
Bit:
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
AO
Mnemonic: AUXR
Address: 8Eh
AO:
Turn off ALE signal.
5.10 Reduce EMI Emission
Because of the on-chip ROM, when a program is running in internal ROM space, the ALE will be
unused. The transition of ALE will cause noise, so it can be turned off to reduce the EMI emission if it
is not needed. Turning off the ALE signal transition only requires setting the bit 0 of the AUXR SFR,
which is located at 08Eh. When ALE is turned off, it will be reactivated when the program accesses
external ROM/RAM data or jumps to execute an external ROM code. The ALE signal will turn off
again after it has been completely accessed or the program returns to internal ROM code space.
5.11 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 W78L812 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.
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