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Functional Description
The MVME177 implements Flash write protection through clearing a control bit (GPIO1) in the GPIO register in the VMEchip2, to enable write by the software after download process/ programming is completed.
EPROM
There are two
❏8 bit
❏16 bit, and
❏
The EPROMs as shipped are normally used for the onboard debugger firmware (177Bug), but could be used to download user code to Flash. The EPROMs make up only 1MB of memory, but can share the first 2MB of space with the first 2MB of Flash. The EPROMs occupy only 1MB space in the ROM space in mixed mode and will be repeated in the second 1MB space (which is reserved for future expansion). The EPROMs could coexist with this 2MB of Flash, or could be used to program all 4MB of Flash, then the J8 jumper could be removed to make only Flash available.
After a system reset, the EPROMs are mapped to the default addresses $00000 through $FFFFF, and could be mapped to $FF800000 through $FF8FFFFF if needed. The control between mapping EPROM/Flash mixed mode and all Flash mode is done by the combination of external board jumper J8 and the VMEchip2 bit GPIO2. Table