MC96FM204/FM214
64
April 7, 2016 Ver. 1.8
10. Interrupt Controller
10.1 Overview
The MC96FM204/FM214 supports up to 14 interrupt sources. The interrupts have separate enable register bits
associated with them, allowing software control. They can also have four levels of priority assigned to them. The
non-maskable interrupt source is always enabled with a higher priority than any other interrupt source, and is not
controllable by software. The interrupt controller has following features:
- Receive the request from 14 interrupt source
- 6 group priority
- 4 priority levels
- Multi Interrupt possibility
- If the requests of different priority levels are received simultaneously, the request of higher priority level
is served first.
- Each interrupt source can be controlled by EA bit and each IEx bit
- Interrupt latency: 3
– 9 machine cycles in single interrupt system
The non-maskable interrupt is always enabled. The maskable interrupts are enabled through four pair of
interrupt enable registers (IE, IE1, IE2, IE3). Each bit of IE, IE1, IE2, IE3 register individually enables/disables the
corresponding interrupt source. Overall control is provided by bit 7 of IE (EA). When EA is set to
‘0’, all interrupts
are disabled: when EA is set to
‘1’, interrupts are individually enabled or disabled through the other bits of the
interrupt enable registers. The EA bit is always cleared to
‘0’ jumping to an interrupt service vector and set to ‘1’
executing the [RETI] instruction. The MC96FM204/FM214 supports a four-level priority scheme. Each maskable
interrupt is individually assigned to one of four priority levels according to IP and IP1.
Table 10-1 shows the Interrupt Group Priority Level that is available for sharing interrupt priority. Priority of a
group is set by two bits of interrupt priority registers (one bit from IP, another one from IP1). Interrupt service
routine serves higher priority interrupt first. If two requests of different priority levels are received simultaneously,
the request of higher priority level is served prior to the lower one.
Table 10-1 Interrupt Group Priority Level
0 (Bit0)
Interrupt
Group
1 (Bit1)
2 (Bit2)
3 (Bit3)
4 (Bit4)
5 (Bit5)
Interrupt 0
Interrupt 6
Interrupt 12
Interrupt 18
Interrupt 1
Interrupt 7
Interrupt 13
Interrupt 19
Interrupt 2
Interrupt 8
Interrupt 14
Interrupt 20
Interrupt 3
Interrupt 9
Interrupt 15
Interrupt 21
Interrupt 4
Interrupt 10
Interrupt 16
Interrupt 22
Interrupt 5
Interrupt 11
Interrupt 17
Interrupt 23
Highest
Lowest
Highest
Lowest
Summary of Contents for MC96FM204
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