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The micro program reads out the
hundreds position of the 1401 instruc-
tion, in this case a 1.
Next, an
address is formed to address local stor-
age.
The micro program uses the hun-
derds digit to form bits 4-7 of the
address, and since this is the hundreds
position, forces the bits 0-3 to a 2
(HEX).
The resultant address 21 in HEX
is used to address local storage. Posi-
tion 21 in local storage brings out a C4
(HEX).
C4 represents the Y bias 60 plus
the binary equivalent of 100 (64 in
HEX).
If the same address, 21, is now
used to address the MPX 1 portion of
local storage, it will bring out the
high-order byte of the address being
formed.
In this case, 21 hrings out 30.
30 represents the Z bias plus 00
hundred.
At this point the micro pro-
gram has developed the address 3064
(HEX).
Now the micro pr9gram forms an
address of
ex,
where X is the units
digit of the 1401 address.
In this case
the address is 02 (HEX).
Addressing
local storage with 02 brings out 02,
which is added to 30C4 already stored,
giving new value of 30C6.
Finally, the
«,icro program processes the tens posi-
tion of the 1401 address by forcing a
constant of 1 in the high order of the
local storage address and inserting the
tens digit of the 1401 address in the
low order of the byte.
In this case, 12
is formed to address the tens conversion
table, bringing out a 14 (HEX).
This is
added to 30C6.
The result, 30DA, is
inserted into UV (1401 B-Star).
The
micro program tests to see if it is
forming an A-field address, and if so,
the micro program takes the contents of
UV and inserts it into IT (1401 A-Star).
See Figure 5-4.
TO ADDRESS BUMP
M N
Hrds Low
rn
Hrds High
rn
Units
rn
Tens
rn
Figure 5-4.
CONVERTED 1400 ADDRESS
\ 0 \ 0 \ C \4\ Hrds Low Bias 60 + 100
\3 \ 0 \ C \ 4\ Hrds Hig h Bias 30
+
0 Hrds
1400 System Address
Conversion
Zone bits in the hundreds and units
positions of the 1401 are tested for by
the micro program and are not found in
the address conversion tables (Figure
5-5) •
5-5
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