Transfer Instructions - IBM 7090 Instruction-Reference

The E cycle is used to:
1. Reset the MQ
2. Bring the divisor from storage
3. Set 338 (2710) into the SC (used to count the number of shifts during divide)
4. Divide dividend fraction by 2 by shifting the fraction right one place (to be
used for comparison of dividend fraction to divisor fraction)
First step L time is used to:
1. Determine if dividend fraction is more or less than two times the divisor
fraction
2. Set the MQ(S) to the algebraic sign of the quotient
3. Shift dividend left one place to put dividend back to initial position
4. Check AC fraction for zero
5. Get the difference between divisor and dividend characteristics
6. End operation if the AC fraction is zero or if the dividend fraction is twice
as large or larger than the divisor fraction
7. Reset the whole AC if the AC fraction is zero
Second step L time is used to:
1. Increase the characteristic difference by one if dividend fraction is equal to
or greater than the divisor fraction
2. Shift the dividend fraction left one place if the dividend fraction is less than
the divisor fraction
3. Step the shift counter down to 2610--the desired number of shifts to move a
bit from MQ(35) to MQ(9).
Third step L time is used to do the actual division. The objectives of third step L
time are to:
1. Attempt to reduce the AC fraction by the amount of the divisor fraction
2. If the reduction is successful put a 1 in MQ(35)
3. Shift AC and MQ left one place, step shift counter, and put a 1 in AC(35)
4. Repeat steps 1, 2, and 3 until the SC equals zero
5. Compute the characteristic of the quotient and put it into the MQ
6. End operation when the shifting and reductions are complete
I time of the next instruction is used to:
1. If there was no divide check and the dividend fraction was not zero:
a. AC fraction is re -complemented to get true number
b. Characteristic of the remainder is set to 2710 less than the original
characteristic of the dividend
2. Stop the machine if there was a divide check
Floating Divide or Proceed FDP +0241 (Min I, E, L)
(Max I, E, 12L)
This instruction operates the same as FDH, except that a divide check does not
halt the computer.
5.3.05 Transfer Instructions
Transfer instructions are used to alter the sequence of instructions. The condi-
tional transfers allow automatic testing of problem conditions without stopping the
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