P83C266BDR datasheet(27/92 Pages) PHILIPS

27 / 92 page

1999 Mar 10

Philips Semiconductors

Product speciﬁcation

Microcontrollers for PAL/SECAM TV

with OSD and VST

P8xCx66 family

11.8

Interrupt Polarity Register (IX1)

Writing a logic 1 to bits IL9, IL6, IL5, IL4, IL3 and IL2 will set the polarity level of the corresponding external interrupt to

be active HIGH. Writing a logic 0 to these bits will set the corresponding external interrupt to be active LOW.

External interrupts INT1 and INT0 however can be programmed to be edge sensitive. Writing a logic 1 to bits IL8 and IL7

will activate the external interrupts INT1 and INT0 on a rising edge (LOW-to-HIGH). Writing a logic 0 to bits IL8 and IL7

will activate the external interrupts INT1 and INT0 on a falling edge (HIGH-to-LOW). This feature is useful for pulse width

measurement; see Section 11.8.1.

Table 29 Interrupt Polarity Register (SFR address E9H)

Table 30 Description of IX1 bits

11.8.1

PULSE WIDTH MEASUREMENT EXAMPLE

To determine the LOW time of a signal on the external interrupt pin INT0 the following sequence should be followed.

1. External interrupt 0 must be programmed to edge sensitivity (SFR TCON, address 88H).

2. IL7 must be programmed as shown in Fig.12.

3. The value held in Timer 0 or Timer 1 represents the pulse width of the signal on the INT0 pin.

76543210

IL9

IL8

IL7

IL6

IL5

IL4

IL3

IL2

BIT

SYMBOL

DESCRIPTION

IL9

external interrupt 9 polarity level (P1.7 port line)

IL8

external interrupt 1 polarity level (INT1) polarity level

IL7

external interrupt 0 polarity level (INT0) polarity level

IL6

external interrupt 6 polarity level (P1.4 port line)

IL5

external interrupt 5 polarity level (P1.3 port line)

IL4

external interrupt 4 polarity level (P1.2 port line)

IL3

external interrupt 3 polarity level (P1.1 port line)

IL2

external interrupt 2 polarity level (P1.0 port line)

Fig.12 Pulse width measurement timing diagram.

handbook, full pagewidth

INT0

IL7

INT0(CPU)

Start interrupt service

routine to start counting

system clock periods

with Timer 0 or Timer 1

Start interrupt service

routine to stop counting

of Timer 0 or Timer 1

MGL295

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