MC68LC302 Datasheet, PDF (47/169 Pages) Motorola, Inc – Low Power Integrated Multiprotocol Processor Reference Manual

System Integration Block (SIB)
the stack pointer must point into the 576 bytes if any exceptions
are to be taken within the boot code.
All 68000 accesses to the dual port RAM are visible externally
on the address and data pins so program execution in the 576
byte code space can be monitored.
After the boot process is completed by the user, it is suggested that the user issue the CP
Reset command to the CP command register (CR) before reinitializing the SCCs. This will
return the CP to its original state and eliminate any possible inconsistencies in the initializa-
tion process. The RISC cannot return to boot mode unless a system reset is executed with
the PA7 pin asserted low. Toggling of the PA7 pin when the device is not in system reset is
allowed, and in this mode the PA7 pin can be used in its alternate functions.
NOTE
The user may wish to disable the software watchdog timer (Tim-
er 3) in the initial boot code if a long delay (i.e. more than 10 sec-
onds) can occur between the initial boot download and the rest
of the download process.
At the end of the Boot from SCC function, the following registers contain values that differ
from their default reset values:
ICR = 0xc000
BAR = 0x0000
SCON1 = depends on mode.
The SCM1 register is reprogrammed to its reset value of 0x0
NOTE
During the Boot from SCC procedure no external master should
acquire the bus.
3.4 DMA CONTROL
The IMP includes seven on-chip DMA channels, six serial DMA (SDMA) channels for the
three serial communications controllers (SCCs) and one IDMA. The SDMA channels are
discussed in the MC68302 User’s Manual. The IDMA is discussed in the following para-
graphs.
3.4.1 MC68LC302 Differences
The DREQ, DACK, and DONE pins have been removed. The user must not program the
IDMA for external request generation.
The External Bus Exceptions, BERR and Retry, have been removed. Only HALT or an in-
ternal BERR generated by the Hardware Watchdog Timer is supported.
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MC68LC302 REFERENCE MANUAL
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