Sel device #4 - RAND JANUARY

Not ready ~

Ready

t

Connect input

I

~

_1.10

Steps

Ready

+

I

_input

Connect Steps 11+15

i

Ready Of

I

input Connect

Steps 16 .. 25

+

Ready t

track 1

track 2

track 3

C onnect Input track

I .

₄

Steps 26 .. 48

~

v -

The program necessary to accomplish the above is:

r-RCEMAND IN FROM

I

DEMAN D OU T TO

INPUT I ^{OU TPU T} ^NO. TYPE OF UNIT TO SCAN OU T NO

I ^I ^I ¹ .50, ⁹

1

2 SOz ¹⁰

3 S()~ 11

4 504 ¹²

5 13

6 ¹⁴

7 15

I

^S~~RT

_I

DI.:4:~

I

SCAN OUTS 8 ₁₆

NO. TO

I III ~r-A" I 2. _" ,. 1/

3 " ^II Ib

'-I

..

_Zb

This program accomplishes the following:

When the start button is pressed we Demand Unit #8 which, since it is acting as a multiplexer for units 1 - 4, scans unit 1. If unit 1 is ready we proceed through steps 1 thru 10. At the end of step 10 the exit of the step rede-mands unit #8 and unit 2 is scanned. If unit 1 was not ready the next unit (unit 2) would automatically be scanned.

After unit 4 is scanned and found not ready we obtain a pulse from the "demand out" which is wi red back to the

"demand in" to repeat the cycle beginning with unit ^# 1.

v -

DJ;/tIt~NO ^UNIT"'8 fr1vJ..JJPLEX AOAPTER . R...J.J6J3Oq~O

v -

As can be seen by the dotted lines in the diagram, the computer Scan-Out hubs on the multiplex adapter plugboard are internally connected with the "Scan Out" hubs on the computer plugboard.

Thus the scan unit multiplex exits emit current when the particu-lar device is ready to be processed and the computer is connected to the related input track. This current comes out of the compu-ter plugboard routine scan out assignment hubs and is directed through external wires to the appropriate step. The completion of a devices routine re-demands the MUltiplex adapter and tells it to test the next unit and so on. Of course if any unit in the sequence is not ready to be processed the multiplexer auto-matically moves on and tests the next device in sequence.

As can be seen there are only six (6) routine assignment hubs for each multiplex adapter although each adapter can handle up to 24 devices. This should not present a problem since it is rare that more than 6 routines would be required in anyone processing run. However, should such a case occur, selector techniques could be used to effectively expand the routine possi-bilities.

SCAN GROUND

It may often be true that the input device routines overlap in certain steps of the program. Thus some means of branching step exits on the basis of what routine is effective at the time is needed. Scan ground provides a means of accomplishing this in a very direct manner. Scan ground is merely a ground function which is controlled by the routine used. Thus, on the computer plugboard, there is a scan ground exit hub for each scan out hub. Their use might be best shown by an example:

Assume that in the last case we want:

Device In At Out At

No. Step_ Step_

1 1 10

2 7 12

3 11 26

4 20 48

v -

As can be seen there are step overlaps between each devices routine, these may be flow charted as:

Scan out 1 Step

t

.. 2

I t 3

It 4

,. 5 .. 6 Step 7

It 8

" 9

tt 10

Step 11 Step 12

Step 13

I I

Step I 19 Step 20

I I I I

Step' 26

Step 27

Step' 48 01 #8

~

Scan out 2 Scan out 3 Scan out 4

D1 #8

01 #8

-

---V-80

The flow chart clearly points out that we must select the exits of steps 10, 12, and 26 on the basis of which routine is being processed.

The selector programming for this is:

- _-

"----PICK-UP FROM GROUND _TO Tit SELECT COMMON NON-SELECT 1

5H

^56, ¹ PI *'8 P8::J/VI.:5r* 10 :IN:5r" II

5/-1 SG.z. ² z:>Ir#8 ^II ^{.. ;#}IZ ^fa

" *'

¹³

30 DI#8 _" ^{.. i U} .. ^{I I}-:/&27

51-/ _SG.5

---"""

---The fact that selector hold is wired to the pickup of the three selectors indicates that current is entering each selector pickup at all times during the program. However, since the selector grounds are wired to scan ground, the circuit will be completed

(and the selector transferre~ only when the appropriate device is connected to the computer through the multiplex adapter, thus allowing the selector hold pulse to get to ground.

v -

⁸¹

The wiring for these selectors would be:

,

IMM.OO 14

E

-IN ^{13 0}0 : ⁰15 _'If 0 IMM.O.O 16

n

⁰¹⁷

' - DDRESS + OHOW NO CHECK

~Oo--oo--oOOO

~ o ⁰ ¹⁸⁰

1 ~ 25 STEP CLEAR

"" 0 0---<>---<>--1 ⁰ ⁰

~ 2 2~ IN OUT

5 """""0 ^{1 0} A'~l ⁰ Bl~l ^{0 CO} ⁰

13 3 27 IN OUT IN OUT IN ~

Z O O 20 0 20 0 20 10 0

~ 4 '"II Ve:.

STEP IN

I

p 0250 ~O I ~ "'

"""-IN OUT

~

p 0.26.

""

=>~

p ~ <Ii 0 I ^d

° ⁰²⁸⁰^I^do! ⁰

. READ 1

In summary, note the following facts concerning the 'Scan Multi-plex" mode of operation.

1) One demand unit is required to act as a multiplex adapter for the scan units.

2) Only six scan out hubs are available for all scan units included in a system.

3) The demand unit appropriated to act as a multiplex

adapter for the scan units serves the following purposes:

a) The Demand "In" hub starts the sequential scan of the input devices when it receives a pulse. The unit the scan begins on is always the unit following the last one processed by the computer.

v -

⁸²

B. DEMAND PROGRAMMING

In the preceding section the "Scan Multiplex" mode of operation was discussed. In this portion the other mode of input-output device control available with the Univac File-Computer is covered. It should be noted that either or both modes of con-trol can be utilized in one program.

Scan Control is a technique whereby the input device informs the computer that it is ready to be processed. In other words the input device controls the computer. Obviously such an arrange-ment is not satisfactory for programs which require activating an input-output device on the basis of a condition arising in directly interrogated and activated by the program itself, rather

than by automatic multiplex scanning.

Before illustrating the use of Demand controlled input-output units, the functions of the plugboard hubs related to each demand

Dans le document RAND JANUARY (Page 193-200)