70
3.3.4
Internal Interrupts
There are 17 internal interrupts that can be requested by the on-chip peripheral modules. When a
peripheral module requests an interrupt, the corresponding bit in IRR1 or IRR2 is set to 1.
Individual interrupt requests can be disabled by clearing the corresponding bit in IENR1 or IENR2
to 0. All interrupts can be masked by setting the I bit in CCR to 1. When an internal interrupt
request is accepted, the I bit in CCR is set to 1. Vector numbers 10 to 20 are assigned to these
interrupts. Table 3.2 shows the order of priority of interrupts from on-chip peripheral modules.
3.3.5
Interrupt Operations
Interrupts are controlled by an interrupt controller. Figure 3.2 shows a block diagram of the
interrupt controller. Figure 3.3 shows the flow up to interrupt acceptance.
Interrupt controller
Priority decision logic
Interrupt
request
CCR (CPU)
I
External or
internal
interrupts
External
interrupts or
internal
interrupt
enable
signals
Figure 3.2 Block Diagram of Interrupt Controller
Interrupt operation is described as follows.
1. When an interrupt condition is met while the interrupt enable register bit is set to 1, an
interrupt request signal is sent to the interrupt controller.
2. When the interrupt controller receives an interrupt request, it sets the interrupt request flag.