RCA 301 Programmer's Reference Manual
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In most cases, the entire A address refers to a HSM location, and the entire B address refers to another HSMlocation. In some instructions, however, only a portion of the A address or B address is used, or one part of theaddress may designate one value and the other part another value. The components of the A address are referredto as An, A15 A2, A,, and the components of the B address as B„, B„ B,, B3.In instructions where the N character is used as a count, the number of the count may be from 0 to 44. As theN character can only contain one character, the following symbols are used to designate the N character for countsfrom 0 to 44:N Count Symbol N Count Symbol N Count Symbol N Count Symbol0 0 11 A 22 K 33 T1 1 12 B 23 L 34 U2 2 13 C 24 M 35 V3 3 14 D 25 N 36 W4 4 15 E 26 O 37 X5 5 16 F 27 P 38 Y6 6 17 G 28 Q 39 Z7 7 18 H 29 R 40 EB8 8 19 I 30 »> 41 , (comma)9 9 20 — ( minus) 31 / 42 %10 & 21 J 32 S 43 • (ISS)44 =Storage of InstructionsInstructions are stored sequentially in the High Speed Memory. Each instruction is stored in ten consecutivememory locations (5 diads) so that the Operation Code is placed in the first character of a diad.StaticizingAn instruction can be interpreted and executed by Program Control only after it has been brought out of theHigh Speed Memory locations in which it has been stored, and its components placed in the proper registers. Thisprocess is called "staticizing" and is accomplished in five status levels.A status level lasts for seven microseconds and is a term applied to a series of pulses which open certain pathsover which information can travel. Each status level has a specific function. In staticizing each instruction, the firststatus level brings the first diad (two characters) of the ten character instruction (ONAAAABBBB) into theMemory Register and automatically regenerates the characters in their original location in the HSM.The O character is then sent to the NOR Register, and the N is sent to the N Register. This completes thefirst status level. The^ second status level brings the next diad (A0, A,) into the memory register, regenerates thecharacters, and sends the A0, A, characters to the A Register. During the third status level the A2, A3 charactersare transferred in a similar manner, and the fourth and fifth status levels transfer B0, Bj and B2, B3 to the B AddressRegister.The total staticizing time is 35 micrbseconds, and is constant for every instruction, even when the N count iszero. The number of status levels involved, and their sequence for execution (after staticizing) of a given instruction,depends upon what must be accomplished by that instruction.Direct and Indirect AddressingWhen the least significant character of an address is written as a number, i.e., the zone bits are 00, the addressis a direct address. Direct addresses establish the initial register settings for instructions in which they are employed.III-2 |
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