Clock Ring
A clock ring
is
a free-running binary trigger ring consisting
of
a number
of
polarity hold latches connected
in
series. The
output
of
one latch
is
the
input
to
the
next latch.
Clock Ring
REG
---1+1
Input
+1
r1.Ilftru1.n.fl
Clock 1
Clock2
Clock 1
~
Clock3
Clock2~
'---~
Clock3~
Parity Generator (PG)
This block generates a parity
(P)
bit to keep
the
bit
count
odd.
Read only storage and read/write storage - The symbol
for
the
functional block
is
MREG.
An
MREG
block with
buffered
output
is
labeled MREGB.
Address lines - Address lines are identified by line
function symbol
A.
The active bits
in
these lines select
the positions
to
be accessed. The number
in
parentheses
above the input group indicates the number
of
lines
that
must be active
to
get
an
active output. Activating
the
o line selects addresses 0 through 127. Activating
the
128
line selects addresses 128 through 255.
R/W
(read/write control) line - The
R/W
(read/write
control line causes a read operation
to
be
performed
when the line
is
at
the
indicated polarity, and a write
operation when
the
line
is
at
the
opposite polarity.
Output
buffer reset line (RB) - The
output
buffer reset
line, when it
is
at
the indicated polarity, resets
the
output
buffer.
Address
----(0-71
Low Order Select
__
-I
High Order
Select--
....
Device Select
-----I
Read
or
Write -
__
--I
Output
Gate
--_--I
Reset
Output
Buffer
Data
In
____
(0-7)
5-12
MREGB
Line Function Symbols
(0-1)
_Data
Out
BUNDLING OF SIGNAL LINES
Bundling groups signal lines together
that
represent buses,
and
in
some cases, similar functions, or similar sources
(block output) and sinks (block input).
Each line (strand)
is
identified both
at
the
point it enters
the bundle and
at
the
point it leaves
the
bundle. A single
line
that
crosses
the
bundle
is
not
identified,
as
shown
in
the following illustration:
Strands
Enter a
Bundle
o
2
3
4
-----11------
Line Crossing a Bundle
Note: Logic lines always enter a bus from
the
left and
exit a bus on the right. The active level
of
each line
is
shown
at
its source logic block or by its line name.
All
lines
of
a particular bundle might
not
have
the
same
active level.
/'
\,
\
/
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