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PCCchip2

C040

CPU040. This bit should remain set to indicate that the

 

MPU is from the M68000 family. When the bit is set,

 

EIPL<2..0>are driven as outputs which carry the

 

priority encoded interrupt request from the PCCchip2

 

interrupt sources. When the bit is cleared, EIPL<2..0>

 

are not driven as outputs, but are inputs only.

DR0

Download ROM at 0 (not applicable to MVME1X7P).

 

This bit should remain cleared, so that DROM appears

 

only in its normal address range. (When DR0 is set,

 

DROM also appears at $00000000 through $0001FFFF.)

 

DR0 is cleared by power-up or local reset, but if no other

 

device responds (within a certain amount of time) to the

 

first memory access after the reset, then the PCCchip2 sets

 

DR0. This causes the DROM to respond to the memory

 

access (and all memory accesses thereafter until software

 

clears DR0).

Note

V=1 if no other device responds to the first memory access

 

after Power-up or Local Reset. Otherwise V=0.

Vector Base Register

The Interrupt Vector Base Register is located at $FFF42003. It is an 8-bit read/write register that is used to supply the vector to the MPU during an interrupt acknowledge cycle for: the two internal tick timers, LAN interrupt, LAN BERR interrupt, SCSI interrupt, GPIO interrupt, and parallel port interrupts. Only the most significant four bits are used. The least significant four bits encode the interrupt source during the acknowledge cycle. The exception to this is that after reset occurs, the interrupt vector passed is $0F, which remains in effect until a write is generated to the Vector Base Register.

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Computer Group Literature Center Web Site

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Image 214
Motorola MVME1X7P manual Vector Base Register, DR0