IBM 610 Manual Of Operation

Also see for 610: Technical overview and introduction

CONTROL DEVICES 37board keys at the same time and must not be done.An impulse from a source hub used to performtwo tasks (e. g., impulse a function hub and pick upa selector) should not be wired directly to both ofthe hubs. Instead, a single wire should connect thesource hub to the center hub of a distributor andthe two tasks will be performed by wiring from thetwo end hubs of the distributor.Response Class Control HubsBetween the two groups of selectors is a set of hubslabeled resp. These hubs make it possible to controlthe response of the program tape reading unit to theinstructions punched in a particular section of theprogram tape. If one of the c (common) hubs inthis group is connected to one of the class hubs (sayclass 1) the program tape reader will respond to in-structions in the tape identified with class Mark 1.In order that this may be a variable condition, theconnection is usually made through a selector.For example, suppose we wish the computer to re-spond to a certain section of the program tape if, andonly if, the contents of register 14 are negative. Thissituation would arise in the case, mentioned earlier,the solution of the quadratic equation. If the contentsof register 14 were the discriminant (b^ - 4ac), thesection of the program tape in question would con-tain the instructions for dealing with the case of com-plex roots. Suppose further that when the tape waspunched, all the instructions in this section werepunched in class 2. The control panel would be wiredas shown in Figure 3 S.On program steps C-6 and C-7, storage register14 is selected. If the contents of 14 are negative, anelectrical connection is established between C and —terminals of the balance test relay; if positive, be-tween C and + terminals. On program step C-8,the common terminal of the balance test relay is im-pulsed. If the contents of 14 are negative, this impulsetravels through the balance test relay to the puterminal of selector 1. When the pu terminal is im-pulsed, the c and T termiinals of this selector areconnected. If the contents of register 14 are posi-tive, the impulse travels through the balance testrelay to the do terminal of selector 1. When the doterminal is impulsed, the c and n terminals of this se-lector are connected, thus assuring that c and t are not9 10 II 12 13 14Figure 3 5. Response Class Controlconnected. If the register contents are negative and thec and T terminals are connected, this connection canthen be used as a portion of the path connecting thecommon and the class 2 hubs in the group of classresponse hubs. Under these conditions, the computerresponds to class 2 instructions on the program tapeuntil the selector is dropped out.For proper control panel action, it is necessary thatthe response switches on the keyboard be set cor-rectly.Assume that the main program has been punchedin class 0, and that the portion of the program wewish to use as the result of a number being negativeis punched in class 2. On the keyboard the switchis set ON, the 1 switch is set off, the 2 switch is set tocontrol panel, and the 3 switch is set to off.Control panel response class control will be electiveonly if response class switches are set in the control-panel position.