Interrupt Control Unit 8-17
8.3.3 INT4 Control Register (I4CON, Offset 40h)
(Master Mode)
The Am186ER and Am188ER microcontrollers provide INT4, an additional external
interrupt pin. This input behaves like INT3–INT0 on the 80C186/188 microcontroller with
the exception that INT4 is only intended for use as a nested-mode interrupt source.
This interrupt is assigned to interrupt type 10h. The Interrupt 4 Control Register (see Figure
8-6) controls the operation of the INT4 signal.
Figure 8-6 INT4 Control Register (I4CON, offset 40h)
The value of I4CON at reset is 000Fh.
Bits 15–5: Reserved—Set to 0.
Bit 4: Level-Triggered Mode (LTM)—This bit determines whether the microcontroller
interprets an INT4 interrupt request as edge- or level-sensitive. A 1 in this bit configures
INT4 as an active High, level-sensitive interrupt. A 0 in this bit configures INT4 as a Low-
to-High, edge-triggered interrupt. In either case, INT4 must remain High until it is
acknowledged.
Bit 3: Mask (MSK)—This bit determines whether the INT4 signal can cause an interrupt.
A 1 in this bit masks this interrupt source, preventing INT4 from causing an interrupt. A 0
in this bit enables INT4 interrupts.
This bit is duplicated in the Interrupt Mask Register. See the Interrupt Mask Register in
section 8.3.11 on page 8-25.
Bits 2–0: Priority (PR)—This field determines the priority of INT4 relative to the other
interrupt signals, as shown in Table 8-3, “Priority Level,” on page 8-15.

Note: The INT4 pin is multiplexed with PIO 30. To enable the pin t o function as an interrupt,

the PIO mode and PIO direction settings for the INT4 pin must be set to 0 for normal

operation. For more information, see Chapter13, “Programmable I/O Pins.”

15 70
MSK
LTM
Reserved
PR2
PR1
PR0