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MVME5100 Single Board Computer Programmer's Reference Guide

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3<br />

System Memory Controller (SMC)<br />

ROM/Flash Interface<br />

The SMC provides the interface for two blocks of ROM/Flash. Each block<br />

provides addressing and control for up to 64MB. Note that no ECC error<br />

checking is provided for the ROM/Flash.<br />

The ROM/Flash interface allows each block to be individually configured<br />

by jumpers and/or by software as follows:<br />

1. Access for each block is controlled by three software programmable<br />

control register bits: an overall enable, a write enable, and a reset<br />

vector enable. The overall enable controls normal read accesses.<br />

The write enable is used to program Flash devices. The reset vector<br />

enable controls whether the block is also enabled at $FFF00000 -<br />

$FFFFFFFF. The overall enable and write enable bits are always<br />

cleared at reset. The reset vector enable bit is cleared or set at reset<br />

depending on external jumper configuration. This allows the board<br />

designer to use external jumpers to enable/disable Block A/B<br />

ROM/Flash as the source of reset vectors.<br />

2. The base address for each block is software programmable. At reset,<br />

Block A’s base address is $FF000000, if Bank A is less than or<br />

equal to 8MB; otherwise, it is 0xF4000000. Block B’s base address<br />

is $FF800000.<br />

As noted above, in addition to appearing at the programmed base<br />

address, the first 1MB of Block A/B also appears at $FFF00000-<br />

$FFFFFFFF if the reset vector enable bit is set.<br />

3. The assumed size for each block is software programmable. It is<br />

initialized to its smallest setting at reset.<br />

4. The access time for each block is software programmable.<br />

5. The assumed width for Block A/B is determined by an external<br />

jumper at reset time. It also is available as a status bit and cannot be<br />

changed by software.<br />

3-14 <strong>Computer</strong> Group Literature Center Web Site

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