Motorola MVME2300 Series User Manual
Page 177
Functional Description
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2. The base address for each block is software programmable. At reset,
Block A’s base address is $FF000000 and Block B’s base address is
$FF400000.
As noted above, in addition to appearing at the programmed base
address, the first 1Mbyte of Block A/B also appears at $FFF00000-
$FFFFFFFF if the reset vector enable bit is set.
3. The assumed size for each block is software-programmable. It is
initialized to its smallest setting at reset.
4. The assumed device type for Block A/B is determined by an
external jumper at reset time. It also is available as a status bit and
cannot be changed by software.
When the width status bit is cleared, the block’s ROM/Flash is
considered to be 16 bits wide, where each Falcon interfaces to 8 bits.
In this mode, the following rules are enforced:
a. Only single-byte writes are allowed (all other sizes are ignored).
b. All reads are allowed (multiple accesses are performed to the
ROM/Flash devices when the read is for greater than one byte).
When the width status bit is set, the block’s ROM/Flash is
considered to be 64 bits wide, where each Falcon interfaces with 32
bits. In this mode, the following rules are enforced:
a. Only aligned, 4-byte writes should be attempted (all other sizes
are ignored).
b. All reads are allowed (multiple accesses to the ROM/Flash
device are performed for burst reads).
More information about ROM/Flash can be found in the
section of this chapter.
In order to place code correctly in the ROM/Flash devices, address
mapping information is required.
addresses map to the ROM/Flash addresses when ROM/Flash is 16 bits
wide (8 bits per Falcon).
shows how they map when Flash is 64
bits wide (32 bits per Falcon).