Interrupts
SCI Interrupt
MC68HC(7)05H12
—
Rev. 1.0
General Release Specification
MOTOROLA
Interrupts
65
L
G
R
interrupt service routine, located at the address specified by the contents
of memory location $3FF4 and $3FF5.
4.11 SCI Interrupt
There are five different interrupt flags (TDRE, TC, OR, RDRF, IDLE) that
will cause an SCI interrupt whenever they are set and enabled. These
five interrupt flags are found in the five most significant bits of the SCI
status register SCSR. The actual processor interrupt is generated only if
the I-bit in the condition code register is clear and the enable bit in the
serial communications control register 2 (SCCR2) is enabled. The SCI
interrupt causes the program counter to vector to the address pointed to
by memory locations $3FF2–$3FF3 which contain the start address of
the interrupt service routine. Software in the SCI interrupt service routine
must determine the priority and cause of the SCI interrupt by examining
the interrupt flags and the status bits in the serial communications status
register (SCSR).
4.12 SPI Interrupt
There are two different SPI interrupt flags that cause an SPI interrupt
whenever they are set and enabled. The interrupt flags are in the SPI
status register (SPSR), and the enable bits are in the SPI control register
(SPCR). Either of these interrupts will vector to the same interrupt
service routine, located at the address specified by the contents of
memory locations $3FF0 and $3FF1.
4.13 WAIT Mode
All modules that are capable of generating interrupts in WAIT mode will
be allowed to do so if the module is configured properly. The I-bit is
automatically cleared when WAIT mode is entered. Interrupts detected
on port A are recognized in WAIT modes.