File Number 1620-0EMI Form A26-5569-0 Systems Reference Library IBM 1620 Original Equipment Manufacturers' Information This manual provides non-IBM engineers with sufficient data to attach units of the IBM 1620 System to their equipment. It contains supplemental tie-in data not readily available in other IBM publications, and tables that show characteristics of data and signal lines at the cable connectors. © 1961 by International Business Machines Corporation Address comments regarding the content of this publication to: IBM, Product Publications Department, San Jose, California Contents IBM 1620 Central Processing Unit. .. 5 Lines to the Card Read Punch . .. 24 General Description ................................. 5 Connections with the Card Reader .................. 24 Data and Instruction Format ....................... , 5 Connections with the Card Punch . .. 25 Stored Program .................................. 6 Clutch Controls .................................. 25 Control Keys and Lights ........................... 8 Power Sequencing Interlocks ....................... 25 Input/Output Data and Control Lines ................. 10 Power Supplies ................................... 26 Lines to the 1621 Paper Tape Reader .............. , 10 Lines to the 1622 Card Read Punch ................. 12 IBM 1623 Core Storage Unit. .. 27 Lines to the 1623 Core Storage Unit ................ , 14 General Description ................................. 27 Lines to the 1624 Paper Tape Punch ................ , 16 Connections to the 1623 Core Storage Unit ............ 27 Power Supplies ................................... 17 Signal and Timing Lines . .. 27 IBM 1621 Paper Tape Reader .. .................. , 18 Power Sequencing Interlocks ........................ 29 General Description ................................ , 18 Power Supplies ................................... 29 Keys and Lights ................................. 18 Lines to the 1621 Paper Tape Reader ............ .. 18 IBM 1624 Paper Tape Punch . ..................... 30 General Description ................................. 30 IBM 1622 Card Read Punch . ..................... , 21 Connections to the 1624 Paper Tape Punch ............. 30 General Description ................................. 21 Signal and Data Lines . .. 30 Switches, Keys, and Indicator Lights ................ , 21 Power Supplies ................................... 31 Preface Each of the five sections in this manual is designed to provide all the information on interconnecting lines necessary to attach any of the Rve units of the 1620 Data Processing Unit to non-IBM equipment. The refer­ ences in each section indicate additional sources of information regarding the manner in which the par­ ticular unit operates within the 1620 System. IBM 1620 Data Processing System IBM 1620 Central Processing Unit This section provides data to satisfy the special needs can be addressed individually by a 5-digit address. The of non-IBM engineers who wish to attach other than addressing system provides for the selection of any IBM input/output devices to the 1620 Central Process­ digit or group of digits within core storage. ing Unit. It provides easy access to supplemental tie-in data not so readily available in other IBM publications. Detailed theory and mechanical principles of oper­ Check Bit Numerical Bits ation are not included. These may be found in the fol­ ~ (~ ____-AA ____ ~ lowing IBM publications relating to the 1620 System. Title Form ~ IBM 1620 CE Manual of Instruction 227-5507 Flag Bit IBM 1620 CE Reference Manual 227-5500 IBM Bl Electric Typewriter CE Reference Manual 223-6652 C 8 4 2 IBM 1620 Data Processing System Reference a x Manual A26-4500 1 X Additional engineering information can be obtained 2 X from system diagrams and other available engineering 3 X X X documents. 4 X 5 X X X General Description 6 X X X The IBM 1620 Data Processing System is a solid-state 7 X X X electronic computer system, designed for technological 8 X applications. The system is composed of four separate units as follows: 9 X X X 1620 Central Processing Contains console, process- Unit ing circuitry, input/output typewriter and 20,000 posi­ Figure 1. Bit Positions and Bit Configuration tions of core storage. 1621 Paper Tape Reader Reads 8-channel paper tape. The 1621 also contains space The computer can perform the 32 basic operations for the 1624 Paper Tape listed in Table 1 and several special feature OP codes. Punch. Each operation is specified by a 12-digit instruction 1622 Card Read Punch Contains a buffered card which contains a 2-digit operation code and two 5-digit reader and card punch. addresses (Figure 2). Instructions comprising a pro­ 1623 Additional Core Contains one or two addi- gram are normally stored in consecutive locations in Storage tional blocks of 20,000 posi­ memory and are executed sequentially. tions of core storage. 1624 Paper Tape Punch Eight-channel tape punch. Data and Instruction Format Physically located in the The 1620 is a variable-field length computer. The 1621 unit. shortest admissible field is two digits. The longest can Data and instructions can be entered into the system be any number of digits within the capacity of core from the typewriter, paper tape reader, or card reader. storage. The flag bit (Figure 1) associated with each They are entered in binary-coded-decimal form (BCD) BCD bit is used as a field mark to designate the high­ using the bit configuration shown in Figure 1. Each order position of a numerical field. A flag bit associated of the 20,000 (basic machine) positions of core storage with the units position of a numerical field determines IBM 1620 Central Processing Unit 5 Table I-Operation Codes Q 1°01 °1 I P21 P31 P41 P5 1 P61 Q71 Qal Q9 I 1OIQ111 Arithmetic Instructions CODE Add A2I I--c~~e -I- P Address -I- Q Address---1 Add (Immediate) AM 11 Subtract S22 Figure 2. Instruction Format Subtract (Immediate) SMI2 Compare C24 Compare (Immediate) CMI4 Multiply ~23 are processed from right to left into successively lower Multiply (Immediate) MMI3 memory positions until a digit with a Hag bit is sensed. Records in memory consist of a field or fields of data Internal Data Transmission Instructions related to input/output operations and internal record transmission. A record in memory is addressed at the Transmit Digit TD25 Transmit Digit (Immediate) TDMI5 leftmost (high-order) position, which occupies the Transmit Field TF26 lowest numbered memory position of the record. Rec­ Transmit Field (Immediate) TFMI6 ords are processed serially from left to right into suc­ Transmit Record TR3I cessively higher memory positions. Output and internal record transmission operations are terminated when­ Branch Instructions ever a record mark is sensed. The 1620 System may be programmed so that input Branch B49 occurs in either a numerical or alphabetical mode. Branch No Flag BNF44 Output from core storage to the output device may Branch No Record Mark BNR45 also be programmed in either numerical or alphabetical Branch on Digit BD43 mode. When input or output occurs in a numerical Branch Indicator BI46 mode, each character in core storage is represented Branch No Indicator BNI47 Branch and Transmit BT27 as a single digit occupying one storage position. When Branch and Transmit (Immediate) BTMI7 input or output occurs in an alphameric mode, each Branch Back BB42 character in storage is represented as two digits occu­ pying two adjacent memory positions. Figure 3 illus­ Input/Output Instructions trates the code used. In the alphameric mode, data may consist of numerical, alphabetical, or special Read Numerically RN36 characters. Write Numerically WN38 Each instruction is stored in memory as a 12-digit Dump Numerically DN35 number. The instruction contains a 2-digit operation Read Alphamerically RA37 code and two 5-digit addresses (Figure 2). The func­ Write Alphamerically WA39 tions of the P and Q address portions of the instruction Control K34 are dependent upon the particular operation to be performed. The P part of an instruction may be used Program Control to represent an address in memory of a digit, a field, a record, or another instruction. The part may repre­ Set Flag SF32 Q Clear Flag CF33 sent the address in memory of a digit, a field, a record, Halt H48 or a data field itself. The Q part may also be used in No Operation NOP4I connection with an input/output instruction to specify the address of the I/O device, or the control function to be performed. the sign of the field - no Hag is a plus field, a Hag bit is Stored Program a minus field. A Hag bit is also used in add table storage To solve a problem or to process data, the programmer to indicate a carry. selects a logical sequence of operations from those the A digit in memory occupies one memory position and computer is capable of performing. This series of in­ is addressed individually. Fields in memory consist of structions which designate the operations to be per­ a number of consecutive digits. A field is addressed by formed is called a program. Because the instructions its rightmost (low-order) position which occupies the comprising a program are written into memory from highest numbered memory position of the field. Fields an input device and read from memory for interpreta- 6 Z O'g't tion and execution, the 1620 is called a stored program rr OM " cal ~igit rNumF:Character computer. In order to be interpreted by the computer, each 00 b 03 instruction must be read from memory to registers, The 04 ) high-order digit (00 ) is read first. The readout con­ 10 + tinues through successively higher memory positions 13 $ 14 * until Qll is read, Instructions within a program are 20 - normally executed sequentially (Figure 4). However, 21 / 23 I the sequence may be altered by use of conditional 24 ( branch instructions. 33 - 34 @ INSTRUCTIONS 41 A 42 B The computer can perform the 32 operations listed in 43 C 44 0 Table 1, plus several special feature codes. The instruc­ 45 E tion complement can be divided into five types as 46 F 47 G follows: 48 H Arithmetic. Arithmetic operations are accomplished 49 I 51 J by a table method. Three hundred twenty (320) posi­ 52 K tions of memory are aSSigned for use in arithmetic oper­ 53 L ations.