SAB80C517-M16 SIEMENS [Siemens Semiconductor Group], SAB80C517-M16 Datasheet - Page 161

• Manufacturer Part Number: SAB80C517-M16
• Description: 8-Bit CMOS Single-Chip Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

8.2
As already mentioned above, all interrupt sources are combined as pairs or triplets; table 8-1 lists
the structure of the interrupt sources.
Table 8-1
Pairs and Triplets of Interrupt Sources
External interrupt 0
Timer 0 interrupt
External interrupt 1
Timer 1 interrupt
Serial channel 0 interrupt
Timer 2 interrupt
Each pair or triplet of interrupt sources can be programmed individually to one of four priority levels
by setting or clearing one bit in the special function register IP0 and one in IP1 (figure 8-9). A low-
priority interrupt can itself be interrupted by a high-priority interrupt, but not by another interrupt of
the same or a lower priority. An interrupt of the highest priority level cannot be interrupted by another
interrupt source.
lf two or more requests of different priority levels are received simultaneously, the request of the
highest priority is serviced first. lf requests of the same priority level are received simultaneously,
an internal polling sequence determines which request is to be serviced first. Thus, within each
priority level there is a second priority structure determined by the polling sequence, as follows (see
figure 8-10):
Semiconductor Group
– Within one pair or triplet the leftmost interrupt is serviced first, then the second and third, when
– The pairs or triplets are serviced from top to bottom of the table.
available.
Priority Level Structure
Serial channel 1 interrupt
Compare timer interrupt
162
–
–
–
–
A/D converter interrupt
External interrupt 2
External interrupt 3
External interrupt 4
External interrupt 5
External interrupt 6
Interrupt System