Z8 Encore! XP® 4K Series
Product Specification
54
To avoid missing interrupts, use the following coding style to clear bits in the
Interrupt Request 0 register:
Caution:
Good coding style that avoids lost interrupt requests:
ANDX IRQ0, MASK
Software Interrupt Assertion
Program code can generate interrupts directly. Writing a 1 to the correct bit in the Interrupt
Request register triggers an interrupt (assuming that interrupt is enabled). When the inter-
rupt request is acknowledged by the eZ8 CPU, the bit in the Interrupt Request register is
automatically cleared to 0.
The following coding style used to generate software interrupts by setting bits in the In-
terrupt Request registers is NOT recommended. All incoming interrupts received be-
tween execution of the first LDX command and the final LDX command are lost.
Caution:
Poor coding style that can result in lost interrupt requests:
LDX r0, IRQ0
OR r0, MASK
LDX IRQ0, r0
To avoid missing interrupts, use the following coding style to set bits in the Interrupt Re-
quest registers:
Caution:
Good coding style that avoids lost interrupt requests:
ORX IRQ0, MASK
Interrupt Control Register Definitions
For all interrupts other than the Watch-Dog Timer interrupt, the Primary Oscillator Fail
Trap, and the Watchdog Oscillator Fail Trap, the interrupt control registers enable individ-
ual interrupts, set interrupt priorities, and indicate interrupt requests.
Interrupt Request 0 Register
The Interrupt Request 0 (IRQ0) register (Table 34) stores the interrupt requests for both
vectored and polled interrupts. When a request is presented to the interrupt controller, the
corresponding bit in the IRQ0 register becomes 1. If interrupts are globally enabled (vec-
tored interrupts), the interrupt controller passes an interrupt request to the eZ8 CPU. If
PS022815-0206
Interrupt Controller
ZILOG [ ZILOG, INC. ]
