mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 235

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

11.2.1.2 Freeze Operation
11.2.1.3 QSM Interrupts
MC68HC16Y3/916Y3
USER’S MANUAL
The QSPI and SCI must be brought to an orderly stop before asserting STOP to avoid
data corruption. To accomplish this, disable QSM interrupts or set the interrupt priority
level mask in the CPU16 condition code register to a value higher than the IRQ level
requested by the QSM. The SCI receiver and transmitter should be disabled after
transfers in progress are complete. The QSPI can be halted by setting the HALT bit in
SPCR3 and then setting STOP after the HALTA flag is set. Refer to 5.3.4 Low-Power
Operation for more information about low-power stop mode.
The freeze FRZ[1:0] bits in QSMCR are used to determine what action is taken by the
QSM when the IMB FREEZE signal is asserted. FREEZE is asserted when the CPU16
enters background debug mode. At the present time, FRZ0 has no effect; setting FRZ1
causes the QSPI to halt on the first transfer boundary following FREEZE assertion.
Refer to 4.14.4 Background Debug Mode for more information about background de-
bug mode.
Both the QSPI and SCI can generate interrupt requests. Each has a separate interrupt
request priority register. A single vector register is used to generate exception vector
numbers.
The values of the ILQSPI and ILSCI fields in QILR determine the priority of QSPI and
SCI interrupt requests. The values in these fields correspond to internal interrupt re-
quest signals IRQ[7:1]. A value of %111 causes IRQ7 to be asserted when a QSM in-
terrupt request is made. Lower field values cause correspondingly lower-numbered
interrupt request signals to be asserted. Setting the ILQSPI or ILSCI field values to
%000 disables interrupts for the QSPI and the SCI respectively. If ILQSPI and ILSCI
have the same non-zero value, and the QSPI and SCI make simultaneous interrupt
requests, the QSPI has priority.
When the CPU16 acknowledges an interrupt request, it places the value in the condi-
tion code register interrupt priority (IP) mask on ADDR[3:1]. The QSM compares the
IP mask value to the priority of the interrupt request to determine whether it should
contend for arbitration. QSM arbitration priority is determined by the value of the IARB
field in QSMCR. Each module that can generate interrupt requests must have a non-
zero IARB value, otherwise the CPU16 will identify any such interrupt requests as spu-
rious and take a spurious interrupt exception. Arbitration is performed by means of se-
rial contention between values stored in individual module IARB fields.
When the QSM wins interrupt arbitration, it responds to the CPU16 interrupt acknowl-
edge cycle by placing an interrupt vector number on the data bus. The vector number
is used to calculate displacement into the CPU16 exception vector table. SCI and
QSPI vector numbers are generated from the value in the QIVR INTV field. The values
of bits INTV[7:1] are the same for both the QSPI and the SCI. The value of INTV0 is
supplied by the QSM when an interrupt request is made. INTV0 = 0 for SCI interrupt
requests; INTV0 = 1 for QSPI interrupt requests.
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MOTOROLA
11-3