Astronics RACAL INSTRUMENTS 1260-164AH, Manual, Page: 22 / 28

1260-164AH/BH User Manual Publication No. 980824-164AH/BH Rev. A
Module Operation 3-2 Astronics Test Systems
Operating in
Register-Based
Mode
The 1260-164 offers register-based mode when installed in VXI
platforms that support it. In register-based mode, the 1260-164 is
operated by directly writing and reading to/from ports controlling
four relays each. To access the various registers the following
details must be assembled to generate an absolute address that
can be wrote or read from:
The port and control registers are located in the VXIbus A24
Address Space. The A24 address for a port or control register
depends on:
1. The A24 Address Offset assigned to the 1260-01T module by
the Resource Manager program. The Resource Manager
program is provided by the VXIbus slot-0 controller vendor.
The A24 Address Offset is placed into the “Offset Register” of
the 1260-01T by the Resource Manager.
2. The <module address> of the 1260-164 module. This is a value
in the range from 1 and 12 inclusive.
3. The 1260-164 port or control register to be written to or read
from. Each register on the 1260-164 has a unique offset from
the base address.
The base A24 address for the 1260-164 module may be calculated
by:
(A24 Offset of the 1260-01T) + (1024 x Module Address of
1260-164).
The A24 address offset is usually expressed in hexadecimal. A
typical value of 204000
16
is used in the examples that follow.
A 1260-164 with a module address of 7 would have the base A24
address computed as follows:
Base A24 Address of 1260-164 = 204000
16
+ (400
16
x 7
10
)
= 205C00
16
The port and control registers for Adapt-a-Switch plug-ins and
conventional 1260-Series modules are always on odd-numbered
A24 addresses. For port registers, the 1260-164 reads and writes
to the same location. For control registers, the 1260-164 writes to
one location, but reads back from another. Table 3-1 provides
offsets relative to the base address of the module for all port and
control registers of the 1260-164. To obtain the absolute address
where data is to be written or read from, the base address is added
to the offset:
(Base A24 1260-164 Address) + offset = absolute address
So, for our example base A24 address computed earlier, the
following absolute addresses would apply for the operations
indicated:
205C01 Port A read or written at this location
205E01 ID register read at this location
Before explaining the particulars of reading and writing to port and