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HARDWARE CONFIGURATION
2-24
INTERRUPT
CONTROLLER
Description of Operation
The functions of interrupt controllers are described below.
•
Interrupt functions
The MB89140 series of microcontrollers have 12 inputs for interrupt re-
quests from each resource. The interrupt level is set by 2-bit registers corre-
sponding to each input. When an interrupt is requested from a resource, the
interrupt controller receives it and transfers the contents of the correspond-
ing level register to the CPU. The interrupt to the device is processed as
follows:
(a)An interrupt source is generated inside each resource.
(b)If an interrupt is enabled, an interrupt request is output from each re-
source to the interrupt controller by referring to the interrupt-enable bit
inside each resource.
(c) After receiving this interrupt request, the interrupt controller determines
the priority of simultaneously-requested interrupts and then transfers the
interrupt level for the applicable interrupt to the CPU.
(d)The CPU compares the interrupt level requested from the interrupt con-
troller with the IL bit in the processor status register.
(e)As a result of the comparison, if the priority of the interrupt level is higher
than that of the current interrupt processing level, the contents of the I-
flag in the same processor status register are checked.
(f) As a result of the check in step (e), if the I-flag is enabled for an interrupt,
the contents of the IL bit are set to the required level. As soon as the cur-
rently-executing instruction is terminated, the CPU performs the interrupt
processing and transfers control to the interrupt-processing routine.
(g)When an interrupt source is cleared by software in the user’s interrupt
processing routine, the CPU terminates the interrupt processing.
Figure 2.10 outlines the interrupt operation for the MB89140 series of micro-
controllers.
Internal bus
Register file
IPLA
IR
PS
I
IL
Check
Comparator
MB89140 CPU
(e)
(d)
Enable FF
Source FF
AND
Level
comparator
Interrupt controller
(a)
(b)
(g)
Resource
(c)
(f)
Resource
Fig. 2.10 Interrupt-processing Flowchart
Содержание F2MC-8L Series
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