Xycom XVME-240, Manual

Page: 48 / 73

XVME-240 Manual
October, 1984
Standardized Module I/O Map
The 1K block of short I/O addresses (called the I/O Interface Block) allocated to each
XVME module is mapped with a standardized format in order to simplify programming
and data access. The locations of frequently used registers and module-specific
identification information are uniform. For example, the module identification
information is always found in the first 32 odd bytes of the module memory block --
with these addresses being relative to the jumpered base address (i.e., Module I.D.
data address = base a odd bytes 1H - 3FH). The byte located at base
81H on each module contains a Status/Control register which provides the
results of diagnostics for verification of the module’s operational condition. The next
area of the module I/O Interface Block (base a 82H - roughly l2OF) is module-
specific and it varies in size from one module to the next. It is in this area that the
module holds specific I/O status, data, and pointer registers for use with IPC protocol.
All intelligent XVME I/O modules have an area of their I/O Interface Blocks defined as
“dual access RAM ." This area of memory provides the space where XVME "slave" I/O
modules access their command blocks and where XVME "master" modules could access
their command blocks (i.e., "master" modules can also access global system memory).
The remainder of the I/O Interface Block is then allocated to various module-specific
tasks, registers, buffers, ports, etc.
Figure A-2 shows an address map of an XVME I/O module interface block, and how it
relates to the VMEbus short I/O address space. Notice that any location in the I/O
Interface Block may be accessed by simply using the address formula:
Module Base A Relative Offset = Desired Location
A-3