HC05 datasheet(144/232 Pages) MOTOROLA

144 / 232 page

MOTOROLA

10-10

MC68HC05X16

Rev. 1

RESETS AND INTERRUPTS

10.2.3.1

Miscellaneous register

Note:

The bits shown shaded in the above representation are explained individually in the

relevant sections of this manual. The complete register plus an explanation of each bit

can be found in Section 3.8.

INTP, INTN — External interrupt sensitivity options

These two bits allow the user to select which edge the IRQ and WOI pins are sensitive to as shown

in Table 10-3. Both bits can be written to only while the I-bit is set, and are cleared by power-on or

external reset. Therefore the device is initialised with negative edge and low level sensitivity.

Interrupt sensitivity options selected by INTP and INTN of the miscellaneous register apply to

external interrupt signal, EI. EI is an OR function of all enabled WOI pins (port B and NWOI) and

of the inverted value of the IRQ pin. When one WOI pin is high, it masks any subsequent edge or

level on any other EI pin (IRQ, port B or NWOI).

INTE — External interrupt enable

1 (set)

–

External interrupt (IRQ) and wired-OR interrupt (WOI) enabled.

0 (clear) –

External interrupt (IRQ) and wired-OR interrupt (WOI) disabled.

The INTE bit can be written to only while the I-bit is set, and is set by power-on or external reset,

thus enabling the external interrupt function.

Table 10-3 describes the various triggering options available for the IRQ and WOI pins, however it

is important to re-emphasize here that in order to avoid any conﬂict and spurious interrupt, it is

possible to change the external interrupt options only while the I-bit is set. Any attempt to change

the external interrupt option while the I-bit is clear will be unsuccessful. If an external interrupt is

pending, it will automatically be cleared when selecting a different interrupt option.

Address bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

State

on reset

Miscellaneous

$000C POR

INTP INTN INTE

SFA

SFB

WDOG u001 000u

Table 10-3 IRQ and WOI sensitivity

INTP

INTN

IRQ sensitivity

WOI interrupt sensitivity

Negative edge and low level

sensitive

Positive edge and high level

sensitive

Negative edge only

Positive edge only

Negative edge only

Positive and negative edge

sensitive

Positive and negative edge

sensitive

142

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