Z8FMC04100 ZILOG [Zilog, Inc.], Z8FMC04100 Datasheet - Page 77

• Manufacturer Part Number: Z8FMC04100
• Description: Z8 Encore-R Motor Control Flash MCUs
• Manufacturer: ZILOG [Zilog, Inc.]

PS024604-1005
Interrupt Control Register Definitions
Caution:
Software Interrupt Assertion
Interrupt Request 0 Register
Program code can generate interrupts directly. Writing a 1 to the appropriate bit in the
Interrupt Request Register triggers an interrupt (assuming that interrupt is enabled). This
bit is automatically cleared when the eZ8 CPU vectors to the Interrupt Service Routine
(ISR).
The interrupt control registers enable individual interrupts, set interrupt priorities, and
indicate interrupt requests.
The Interrupt Request 0 (IRQ0) Register, shown in Table 30, stores the interrupt requests
for both vectored and polled interrupts. When a request is presented to the interrupt con-
troller, the corresponding bit in the IRQ0 register becomes 1. If interrupts are globally
enabled (vectored interrupts), the interrupt controller passes an interrupt request to the eZ8
CPU. If interrupts are globally disabled (polled interrupts), the eZ8 CPU can read the
Interrupt Request 0 register to determine if any interrupt requests are pending.
To avoid missing interrupts, ZiLOG recommends the following style of coding to clear
bits in the Interrupt Request 0 Register:
ANDX IRQ0, MASK
The following style of coding to generate software interrupts by setting bits in the Inter-
rupt Request registers is not recommended. All incoming interrupts that are received be-
tween execution of the first LDX command and the last LDX command are lost.
The following code segment is an example of a poor coding style that can result in lost
interrupt requests:
LDX r0, IRQ0
OR r0, MASK
LDX IRQ0, r0
To avoid missing interrupts, ZiLOG recommends the following style of coding to set
bits in the Interrupt Request registers:
ORX IRQ0, MASK
P R E L I M I N A R Y
Z8FMC16100 Series Flash MCU
Product Specification
Software Interrupt Assertion
55