Applications
9-36
MC68360 USER’S MANUAL
MOTOROLA
rupt acknowledge cycle was complete, which defeats the purpose of connecting the IPEND
pin to the BCLRI pin.)
When the QUICC does not need the bus, it will assert the BG pin to the MC68EC040 con-
tinually, improving the MC68EC040 memory access performance.
9.4.1.6 BREAKPOINT GENERATION
. In MC68EC040 companion mode, the QUICC can
be used to generate a breakpoint signal using its breakpoint address register. This register
will respond to QUICC or MC68EC040 accesses, but only the first access of an
MC68EC040 burst access.
The result of a breakpoint is the assertion of the BKPTO pin on the QUICC. In this applica-
tion, it was decided to route this output back to an interrupt input on the QUICC and generate
a nonmaskable interrupt to the MC68EC040. If the MC68EC040 encounters the breakpoint
trap, it will respond with a breakpoint acknowledge cycle. The QUICC does not recognize
this cycle and takes no action.
9.4.1.7 BUS MONITOR FUNCTION
. In MC68EC040 companion mode, the QUICC will
monitor the bus for bus cycles that are not properly terminated. The cycles can originate
from the QUICC or the MC68EC040. If the MC68EC040 originates such a cycle and that
cycle times out without a TA or TEA occurring, the QUICC will assert TEA back to the
MC68EC040 to end the cycle.
9.4.1.8 SPURIOUS INTERRUPT MONITOR
. In MC68EC040 companion mode, the QUICC
will watch for spurious interrupt cycles generated by the MC68EC040, but only on the inter-
rupt levels that the QUICC supports internally (e.g., the levels used by the SIM60 and the
level of the CPM). If such a condition occurs, TEA will be asserted by the QUICC.
9.4.1.9 SOFTWARE WATCHDOG
. If desired, the MC68EC040 can program the QUICC
software watchdog to generate a level 7 interrupt or a system reset. In this application, the
software watchdog is configured in software to generate a reset so that the breakpoint logic
can use level 7 interrupts. No additional hardware is required because the connection
between the reset pins of the QUICC and the MC68EC040 is already made.
9.4.1.10 PERIODIC INTERVAL TIMER
. If desired, the MC68EC040 can use the periodic
interval timer on the QUICC to generate a system interrupt, such as for a real-time kernel.
No additional hardware is required for this function.
9.4.1.11 MC68EC040 CACHING CONFIGURATION
. The MC68EC040 can cache or not
cache data and can program memory as desired. However, it is strongly advisable not to
cache the data that is accessed by the QUICC serial channels because of the overhead
incurred every time a cached data area is written.
The MC68EC040 can decide to cache or not cache 16-byte portions of a bank of memory
on a dynamic basis by using a software technique summarized in 9.5 Selecting Cache
Modes on the MC68EC040.
9.4.1.12 MC68EC040 SNOOPING
. The snooping function is not supported since only one
active processor exists in the system and the QUICC data buffers are not cached.