W78E54C/W78E054C

Publication Release Date: October 3, 2006

- 7 -

Revision A4

Eight-source interrupt information

INTERRUPT SOURCE

VECTOR

ADDRESS

POLLING

SEQUENCE WITHIN

PRIORITY LEVEL

ENABLE

REQUIRED

SETTINGS

INTERRUPT

TYPE

EDGE/LEVEL

External Interrupt 0

03H

0 (highest)

IE.0

TCON.0

Timer/Counter 0

0BH

1

IE.1

-

External Interrupt 1

13H

2

IE.2

TCON.2

Timer/Counter 1

1BH

3

IE.3

-

Serial Port

23H

4

IE.4

-

Timer/Counter 2

2BH

5

IE.5

-

External Interrupt 2

33H

6

XICON.2

XICON.0

External Interrupt 3

3BH

7 (lowest)

XICON.6

XICON.3

5.2.2

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

P4, #0AH

; Output data "A" through P4.0

−P4.3.

MOV

A, P4

; Read P4 status to Accumulator.

SETB

P4.0

; Set bit P4.0

CLR

P4.1

; Clear bit P4.1

5.2.3

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, W78E054C 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 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.