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Register Addressing in the VXIbus Environment
Logical Address
A16/A24 Memory
Mapping
58 Register Programming
Each module in a VXIbus (VXI) system, whether VXI or M-Module, must
have a unique logical address. The HP E2251 Carrier provides a logical
address for each installed M-Module. Refer to the HP E2251 Installation and
Wiring Manual for details (if you are using a different carrier, refer to that
carrier's documentation for register-based addressing information).
The VXI Specification allows for only 64 bytes of address space in A16
memory. However, the M-Module Specification defines 256 bytes of
address space. To resolve this conflict, the HP E2251 Carrier provides two
memory segments for each installed M-Module. The first is in the VXI A16
memory space and contains the standard VXI registers. The second memory
segment is in the VXI A24 memory space and contains all other M-Module
registers (these registers are described starting on page 66). Figure 4-2
shows the A16/A24 mapping for a typical M-Module.
Note
The M-Module's ID word (from the ID EEPROM) is mapped into the
VXI Manufacturer ID Register at address 00
VXI Device Type word is mapped into the VXI Device Type Register at
address 02
h
Figure 4-2. A16/A24 Register Mapping
and the M-Module's
h
Chapter 4
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