Motorola MVME1X7P manual Lcsr Programming Model

LCSR Programming Model

You program a VMEbus slave map decoder by loading the starting address of the segment into the starting address register and the ending address of the segment into the ending address register. If the VMEbus address modifier codes indicate an A24 VMEbus address cycle, then the upper eight bits of the VMEbus address are forced to 0 before the compare. The address modifier select register should be programmed for the required address modifier codes. A VMEbus slave map decoder is disabled when the address modifier select register is cleared.

The address translation registers allow local resources to have different VMEbus and local bus addresses. Only address bits A31 through A16 may be modified.

The address translation registers also provide the upper eight local bus address lines when an A24 VMEbus cycle is used to access a local resource. The address translation register should be programmed with the translated address and the address translation select register should be programmed to enable the translated address. If address translation is not desired, then the address translation registers should be programmed to 0.

The address translation address register and the address translation select register operate in the following way: If you set a bit in the address translation select register, then the corresponding bit in the address translation address register drives the appropriate local bus address line. If you clear the bit in the address translation select register, then the corresponding VMEbus address line drives the appropriate local bus address line. The most significant bit of the address translation select register corresponds to the most significant bit of address translation register and to A32 of the local bus and A32 of the VMEbus.

In addition to the address translation method previously described, the VMEchip2 as used on the MVME1X7P includes an adder which can be used for address translation. When the adder is enabled, the local bus address is generated by adding the offset value to the VMEbus address lines VA<31..16>. The offset is the value in the address translation/offset register. If the VMEbus transfer is A24, then the VMEbus address lines VA<31..24> are forced to 0 before the addition. The adders are enabled by setting bit 11 for map decoder 1 and bit 27 for map decoder 2 in register

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