MC68711E20CFNE3 Datasheet, PDF (87/242 Pages) –

Table 5-3. Highest Priority Interrupt Selection
PSEL[3:0]
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
Interrupt Source Promoted
Timer overflow
Pulse accumulator overflow
Pulse accumulator input edge
SPI serial transfer complete
SCI serial system
Reserved (default to IRQ)
IRQ (external pin or parallel I/O)
Real-time interrupt
Timer input capture 1
Timer input capture 2
Timer input capture 3
Timer output compare 1
Timer output compare 2
Timer output compare 3
Timer output compare 4
Timer input capture 4/output compare 5
Interrupts
5.5 Interrupts
The MCU has 18 interrupt vectors that support 22 interrupt sources. The 15 maskable interrupts are
generated by on-chip peripheral systems. These interrupts are recognized when the global interrupt mask
bit (I) in the condition code register (CCR) is clear. The three non-maskable interrupt sources are illegal
opcode trap, software interrupt, and XIRQ pin. Refer to Table 5-4, which shows the interrupt sources and
vector assignments for each source.
For some interrupt sources, such as the SCI interrupts, the flags are automatically cleared during the
normal course of responding to the interrupt requests. For example, the RDRF flag in the SCI system is
cleared by the automatic clearing mechanism consisting of a read of the SCI status register while RDRF
is set, followed by a read of the SCI data register. The normal response to an RDRF interrupt request
would be to read the SCI status register to check for receive errors, then to read the received data from
the SCI data register. These steps satisfy the automatic clearing mechanism without requiring special
instructions.
M68HC11E Family Data Sheet, Rev. 5.1
Freescale Semiconductor
87