Loading The Memory Map - Xerox 560 Reference Manual

Normally, bit positions 15-31 may be ignored insofar as the
operation of the MMC instruction is concerned. The results
of the instruction are the same whether MMC is indirectly
or directly addressed. However,if MMC is indirectly ad-
dressed and the indirect reference address is nonexistent,
the nona II owed operation trap (location X ' 40 ' ) is activated.
The R field, which must be coded with an even value, des-
ignates an even-odd pair of general registers (R and Ru1)
that contain additional control information required by the
MMC instruction. If the R fi eld is coded with an odd va I
ue
a trap to location X ' 4D ' (instruction exception trap) occurs.
Depending upon the type of addressing, the contents of
register R may be as follows:
If MA
=
0, contents of register Rare:
If MA
=
1 and MM
=
0, the contents of register Rare:
In either case, the Control Image Address is the virtual ad-
dress of a control word within the control image area to be
loaded into a block of memory control registers, as specified
by the contents of register Ru 1.
Depending upon the type of control image being loaded,
the contents of register Ru 1 may be in one of the following
three formats:
For loading memory map image (either a-bit or 11-bit for-
mat), contents of register Ru 1 are:
For loading 4-bit write lock images, contents of register
Ru1 are:
For loading access protection or 2-bit write lock images,
contents of register Ru 1 are:
The Count field (bit positions 0-7) specifies the numberof
words to be loaded from the control image area. If the
initial word count is zero, a word count of 256 is implied.
114 Controi Instructions
The Control Start field (bit positions 15-20, 21, or 22)
points to the beginning of the memory region controlled by
the registers to be loaded. The significance of this field
is different for the 5 modes of MMC operations and is des-
cribed within each mode below.
Affected: (R),(Ru1),
memory control
storage
T raps: Instruction exception,
nonallowed operation.
LOADING THE MEMORY MAP
CONTROL IMAGE
Each word of the memory map control image contains either
four a-bit page addresses or two ll-bit extended page ad-
dresses, as illustrated below:
Typical memory map control image word (a-bit format):
Typical memory map control image word (ll-bit format):
Depending upon the memory map control image format, the
instruction format is one of the following:
LMAP LOAD
MAP
(a-bit format)
LMAPRE LOAD
MAP
REAL EXTENDED (ll-bit format)
Depending upon the type of addressing, the format of regis-
ter R contents is one of the following:
If MA
=
0;
Map
lma~e
Address
I
If MA
=
1
and MM
=
0;