IBM 7090 Instruction-Reference page 136

Development of Program
CONTENTS OF ACCUMULATOR
1-5
6-11
12-17
-23 -29 -35
CAL A(Clear AC, add logical word A)~ 1 3 4 5 8 9
1st
Add B
+6 9 5 9
3
(Unconverted binary sum) =7
onv
CVR 1000, 0, 6
ARS 6
Series of Steps within CVR
Table Next
C(AC) Start
Table C(-) Start Loc
30-35 Loc Refer 1-5 C(-) 21-35
*@
+ 1000 - 1012 1
2
7
12 5 10 17 Count = 5
17 + 1001 - 1018
8 1001 8
2
7
12 5 10
10 + 1001 - 1011 1 1001 1 8 2 7
12
5
5
+ 1001 - 1006 6 1000
6 1 8
2 7 12
12
+
1000 - 1012
2 2 6
1
8
2 7
7 + 1001 - 1008 8 8 2 6 1 8 2
Count = zero: if Tag = 1, 1000 ~RA
SLW C (Store converted BCD sum as logical word)
The execution of CVR requires one L cycle to set the count in the shift counter and
to calculate the initial table location. The instruction is completed in as many E cycles
as specified by the count.
Convert by Replacement from MQ CRQ -0154 (Min I, L) Figure 5.3-72
(Max I, L, 6E)
This instruction operates on the MQ, considered to be composed of six 6-bit repre-
sentations. The instruction replaces a number of these representations equal to the
count of the instruction, with the contents of positions (S-5) of a like number of words
from storage. The location of the first of these storage words is found by adding the
contents of MQ(S-5) to SR(21-35) (intiallythe instruction address portion). Thewordstored
at this modified location is brought to the SR, and the MQ is shifted left six places.
Positions (S-5) of the stored word are placed in MQ(30-35), and the location of the next
storage word is computed by again adding MQ(S-5) to SR(21-35) which is now the ad-
dress portion of the previous storage word. The process continues until the required
number of replacements have been made. At this time the presence of a tag bit in
position 20 of the instruction will cause the address portion of the final storage word
to be stored in index register A.
The following illustrates the use and operation of CRQ:
Prepare a BCD number for printing be replacing leading zeros with blanks:
Convert BCD number 007109 to BL BL 7109
Instructions required for this operation:
LDQ A (BCD number in storage)
CRQ 6,0, 2000 (Convert from MQ)
STQ B (Store converted number)
135
=4
=3
=2
=1
=0