Motorola MVME2300 Series - Manual (Page 215)

Software Considerations
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3
Software Considerations
This section contains information that may be helpful in making efficient
use of the Falcon pair when programming.
Parity Checking on the PowerPC Bus
The Falcon does not generate parity on the PowerPC address or data buses.
Because of this, the appropriate registers in the MPC60x should be
programmed to disable parity checking for the address bus and for the data
bus.
Programming ROM/Flash Devices
Those who program devices to be controlled by the Falcon should make
note of the address mapping that is shown in
Table 3-8 and in Table 3-9 .
When using eight-bit devices, for example, the code will be split so that
every other four-byte segment goes in each device.
Writing to the Control Registers
Software should not change control register bits that affect DRAM
operation while DRAM is being accessed. Because of pipelining, software
should always make sure that the two accesses before and after the
updating of critical bits are not DRAM accesses. A possible scenario for
trouble would be to execute code out of DRAM while updating the critical
DRAM control register bits. The preferred method is to be executing code
out of ROM/Flash and avoiding DRAM accesses while updating these
bits.
Since software has no way of controlling refresh accesses to DRAM, the
hardware is designed so that updating control bits coincidentally with
refreshes is not a problem. An exception to this is the ROW_ADDRESS
and COL_ADDRESS bits. In any event, however, it is not intended that
software write to these bits.