mpc89x58a Megawin Technology, mpc89x58a Datasheet - Page 21

• Manufacturer Part Number: mpc89x58a
• Description: 8-bit Micro-controller
• Manufacturer: Megawin Technology

Interrupt
There are eight interrupt sources available in MPC89x58A. Each interrupt source can be
individually enabled or disabled by setting or clearing a bit in the SFR named IE. This register
also contains a global disable bit (EA), which can be cleared to disable all interrupts at once.
Each interrupt source has two corresponding bits to represent its priority. One is located in
SFR named IPH and the other in IP/XICON register. Higher-priority interrupt will be not
interrupted by lower-priority interrupt request. If two interrupt requests of different priority levels
are received simultaneously, the request of higher priority is serviced. If interrupt requests of
the same priority level are received simultaneously, an internal polling sequence determines
which request is serviced. The following table shows the internal polling sequence in the same
priority level and the interrupt vector address.
The external interrupt /INT0, /INT1, /INT2 and /INT3 each can be either level-activated or
transition-activated, depending on bits IT0 and IT1 in SFR TCON, IT2 and IT3 and XICON.
The flags that actually generate these interrupts are bits IE0 and IE1 in TCON, IE2 and IE3 in
XICON. When an external interrupt is generated, the flag that generated it is cleared by the
hardware. When the service routine is vectored to only if the interrupt was transition –activated,
and then the external requesting source controls the request flag, rather than the on-chip
hardware.
The Timer0 and Timer1 interrupts are generated by TF0 and TF1, which are set by a rollover
in their respective Timer/Counter registers in most cases. When a timer interrupt is generated,
the flag, which generated it, is cleared by the on-chip hardware as soon as the service routine
is vectored to.
The serial port interrupt is generated by the logical OR of RI and TI. Neither of these flags is
cleared by hardware when the service routine is vectored to. The service routine should poll RI
and TI to determine which one to request service and it will be cleared by software.
The timer2 interrupt is generated by the logical OR of TF2 and EXF2. Just the same as serial
port, neither of these flags is cleared by hardware when the service routine is vectored to.
MEGAWIN
External interrupt 0
Timer 0
External interrupt 1
Timer1
Serial Port
Timer2
External interrupt 2
External interrupt 3
Source
MPC89x58A Data Sheet
Vector address
0BH
1BH
2BH
3BH
03H
13H
23H
33H
Priority within level
1 (highest)
2
3
4
5
6
7
8
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