W78LE51C Datasheet, PDF (6/23 Pages) Winbond – 8-BIT MICROCONTROLLER

W78LE51C/W78L051C
2. PORT4
Another bit-addressable port P4 is also available and only 4 bits (P4<3:0>) can be used. This port
address is located at 0D8H with the same function as that of port P1, except the P4.3 and P4.2 are
alternative function pins. It can be used as general I/O pins or external interrupt input sources ( INT2 ,
INT3 ).
Example:
P4
REG 0D8H
MOV
MOV
ORL
ANL
P4, #0AH ; Output data "A" through P4.0−P4.3.
A, P4
; Read P4 status to Accumulator.
P4.#00000001B ; Set P4.0 to be high state
P4.#11111110B ; Clear P4.0 to be low state.
3. Reduce EMI Emission
Because of on-chip Flash EPROM, 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 useless. 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. The AO bit in the
AUXR register, when set, disables the ALE output. In order to reduce EMI emission from oscillation
circuitry, W78L051C allows user to diminish the gain of on-chip oscillator amplifiers 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 effect to external crystal operating improperly at high frequency above 20 MHz. The
value of R and C1, C2 may need some adjustment while running at lower gain.
***AUXR - Auxiliary register (8EH)
-
-
-
-
-
-
-
AO
AO: Turn off ALE output.
4. Power-off Flag
***PCON - Power control (87H)
-
-
-
POF
GF1
GF0
PD
IDL
POF:
Power off flag. Bit is set by hardware when power on reset. It can be cleared by software
to determine chip reset is a warm boot or cold boot.
GF1, GF0: These two bits are general-purpose flag bits for the user.
PD:
Power down mode bit. Set it to enter power down mode.
IDL:
Idle mode bit. Set it to enter idle mode.
The power-off flag is located at PCON.4. This bit is set when VDD has been applied to the part. It can
be used to determine if a reset is a warm boot or a cold boot if it is subsequently reset by software.
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