RadiSys EPC-5A, Справочное руководство по аппаратному и программному обеспечению

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Chapter 6: The VMEbus Interface
Page 69
VME A21-16 Address Register (8130h)
VMEbus Address bits 21-16 Res Res
When an access is performed by the EPC-5A in its window (address range 0E0000h-
0EFFFFh), the access is mapped onto the VMEbus. The least-significant 16 of the
VME address bits are provided directly (from the 486), and the remaining 8 (for an
A24 access) or 16 (for an A32 access) bits must come from somewhere else. Six of
them come from this register. Bit 7 of this register is used as VME address bit 21, bit
6 as VME address bit 20, and bit 2 as VME address bit 16.
The two low-order bits are reserved RAM bits. On writes, assign them the value 0.
For compatibility with EPC-1, this register is aliased at I/O port addresses 8132h,
8134h, and 8136h.
ID Register (8140h & 8141h)
1 1 1 0 1 1 0 0 Lower
1 0 0 A32 1 1 1 1 Upper
This read-only register adheres to the VXIbus specification. It defines the EPC-5A as
a message-based device and the manufacturer as RadiSys Corporation.